Histopathology (Rapini) Flashcards

Question

Erythema dyschromicum perstans / ashy dermatosis

Answer 1

Liquefaction degeneration of the basal layer, colloid bodies, mild or absent Melanin incontinence Perivascular or interface lymphocytes (sparse, early lesions only)

Answer 2

Epidermis normal, rarely necrotic/ulcerated Dermal oedema (often) Perivascular lymphocytes (sometimes around sweat ducts) Thrombi sometimes

Answer 3

Mild vascular dilation with thickened basement membrane and endothelial swelling Arteriolar thrombi (sometimes) Perivascular dermal oedema Sparse perivascular lymphocytes

Answer 4

Epidermis variable: normal, necrotic, vesicular, pustular Vasculitis of small venues with predominant number of neutrophils, sometimes eosinophils, lymphocytes or histiocytes Nuclear dust often Red blood cell extravasation often Thrombi sometimes DIF: IgG, IgM, complement in granular pattern in the superficial blood vessels Fibrin deposits in young or old lesions

Answer 5

Epidermis unremarkable Grenz zone above a diffuse mixed dermal neutrophils, eosinophils, lymphocytes, histiocytes (sometimes plasma or mast cells) Leukocytoclastic vasculitis Haemosiderin in dermis

Answer 6

Epidermis unremarkable Leukocytoclastic vasculitis (less apparent in older lesions) Fibrosis or lipid deposits in older lesions

Answer 7

Epidermis normal, necrotic, or ulcerated Leukocytoclastic vasculitis of small to medium arteries of deep dermis or subcutaneous fat Intimal proliferation and thrombi sometimes Fibrosis in older lesions

Answer 8

Epidermis normal, necrotic, or ulcerated Neutrophilic vasculitis of small vessels Many eosinophils in the dermis Granulomatous inflammation and necrosis within blood vessels and in surrounding dermis and subcutaneous tissue, often palisading Thrombi or extravasated erythrocytes sometimes

Answer 9

Epidermis often necrotic or ulcerated Non-specific perivascular inflammation Vasculitis of small arteries and veins involving neutrophils, lymphocytes, plasma cells and (rarely) eosinophils Granulomatous inflammation in blood vessels and in surrounding dermis often, sometimes palisading Thrombi often, resulting in extensive necrosis Extravasation of erythrocytes

Answer 10

Epidermis normal, sometimes spongiosis of focal parakeratosis Extravasated erythrocytes, endothelial swelling, perivascular lymphocytes Haemosiderin in older lesions

Answer 11

Epidermis normal, necrotic or ulcerated Thrombi and precipitated cryoglobulin in dermal blood vessels Extravasated erythrocytes Sparse perivascular lymphocytes sometimes (not a true vasculitis)

Answer 12

Atrophic epidermis in old lesions (sometimes with hyperkeratosis) Wedge-shaped dermal infarct with broad base toward epidermis Necrotic or absent adnexal structures Mucin in dermis in early red macule, or around edges of early white papules, sclerosis in older lesions Thrombosed arteriole (usually S/C fat) with minimal inflammation, endothelial swelling, or intimal fibrosis

Answer 13

Epidermis with ulceration or pustule formation Diffuse dermal neutrophils, lymphocytes, and/or histiocytes, sometimes with vasculitis

Answer 14

Epidermis necrotic, or ulcerated, occasionally with pustules Pseudoepitheliomatous hyperplasia at the edge of ulcer (sometimes) Diffuse infiltrate of neutrophils, lymphocytes, and histiocytes in the dermis (sometimes with vasculitis)

Answer 15

Atrophic, necrotic, or ulcerated epidermis Hyalinised dermal blood vessel walls prominent Thrombi often Extravasation of erythrocytes Dermal fibrosis in older lesions Sparse perivascular lymphocytes or neutrophils (since inflammation is minimal) DIF of perilesional skin reveals homogenous deposits of immunoglobulins, complement and fibrin in dermal blood vessels

Answer 16

Epidermis is normal or necrotic Subepidermal blister sometimes Thrombi in dermal blood vessels, dermal necrosis in late-stage lesions Extravasated erythrocytes in the dermis Little or no inflammation

Answer 17

Atrophic epidermis (sometimes) Solar elastosis Extravasated erythrocytes in the dermis No inflammation

Answer 18

Follicular plugging Perifollicular erythrocyte extravasation Mild to absent perifollicular lymphocytic infiltrate Haemosiderin in older lesions

Answer 19

Epidermal necrosis Subepidermal blister (sometimes) Thrombi in dermal blood vessels, dermal necrosis Sparse or no inflammation Extravasation of erythrocytes in the dermis

Answer 20

Thrombi of medium sized arteries with occlusion of lumina Ischaemia, necrosis, ulcers Mixed inflammatory cells in vessel walls

Answer 21

Subcorneal pustule of neutrophils Perivascular neutrophils and lymphocytes

Answer 22

Subcorneal pustule, sometimes with eosinophils and neutrophils Perivascular neutrophils, lymphocytes, and eosinophils

Answer 23

Subcorneal vesicle often centred upon a hair follicle, containing mostly eosinophils Perivascular infiltrate of mostly eosinophils

Answer 24

Acantholysis in the epidermis (suprabasal for PV, superficial for PF) None/few necrotic keratinocytes Perivascular lymphocytes, eosinophils, sometimes neutrophils or plasma cells Direct immunofluorescence with IgG and complement within intercellular spaces

Answer 25

Extensive acantholysis through the epidermis (dilapidated brick wall) Dyskeratotic keratinocytes (sometimes) Perivascular lymphocytes, eosinophils absent or rare DIF for immunoglobulins and complement negative

Answer 26

Small foci of acantholysis, usually suprabasal Dyskeratotic cells (acantholytic dyskeratosis) Spongiosis (sometimes) Perivascular lymphocytes (sometimes eosinophils) DIF for immunoglobulins and complement negative

Answer 27

Blister in superficial epidermis (near granular layer) Degenerated keratinocytes adjacent to blister Inflammation mild or absent

Answer 28

Eosinophilic spongiosis (sometimes, especially in early non-blistered red plaques) Subepidermal blister Viable roof over blister, necrotic in old blisters Perivascular lymphocytes and eosinophils, sometimes very sparse (cell-poor pemphigoid) Superficial dermal oedema Microabscesses of neutrophils, eosinophils in the dermal papillae (sometimes) DIF linear IgG (IgG4) and complement deposits in the BMZ (usually roof)

Answer 29

Subepidermal blister seen in some cases or sometimes squamous metaplasia only Viable or eroded roof over the blister Perivascular lymphocytes with variable eosinophils, neutrophils, or plasma cells, if on mucous membrane DIF linear IgG (IgG4) and complement deposits in the BMZ (usually roof)

Answer 30

Spongiosis, sometimes eosinophilic spongiosis, or intraepidermal vesicle Necrotic keratinocyte sometimes (especially basal layer) Marked papillary dermal oedema, subepidermal blister Perivascular lymphocytes with eosinophils DIF linear IgG (IgG4) and complement deposits in the BMZ (usually roof) (complement \> IgG)

Answer 31

Subepidermal blister Sometimes microabscesses of neutrophils in the dermal papillae Perivascular lymphocytes, eosinophils (sometimes) DIF: linear staining of IgA (less often with IgG, IgM or c4)

Answer 32

Neutrophilic micro abscesses in the dermal papillae, few eosinophils Small subepidermal vesicles DIF: granular deposits of IgA in the tips of the dermal papillae

Answer 33

Subepidermal blister Sparse (cell-poor) perivascular lymphocytes Type IV collagen immunohistochemical staining DIF negative except in acquisita (linear IgG and complement in the dermal epidermal junction)

Answer 34

Epidermal necrosis depending on severity Elongated nuclei of keratinocytes in electrical burns Subepidermal blisters Dermal necrosis No inflammation until lesion becomes older

Answer 35

Epidermal necrosis (often) Intra- or more commonly subepidermal bulla Necrosis of adnexa (esp sweat ducts) Dermal necrosis (sometimes) Minimal inflammation except sparse neutrophils in areas of necrosis Negative DIF

Answer 36

Blister varies from sub corneal, intraepidermal to subepidermal Inflammation sparse Negative DIF

Answer 37

Epidermis normal Palisading granulomas around small foci of mild connective tissue degeneration (necrobiosis) and mucin accumulation Single-filing/subtle interstitial pattern of histiocytes between collagen bundles Perivascular lymphocytes (often), sometimes neutrophils or eosinophils are present

Answer 38

Epidermal normal, or atrophic, sometimes ulceration Necrobiotic collagen, often with sclerosis, with palisading granulomas in the dermis often oriented parallel to the epidermis (resembling a layered cake or lasagna) Dermal interstitial infiltrate consists of histiocytes, many multinucleated giant cells, lymphocytes, plasma cells

Answer 39

Palisading granuloma around degenerated connective tissue and fibrin in the deposit deep dermis or subcutaneous tissue Histiocytes and lymphocytes mainly, only a few multinucleated giant cells

Answer 40

Nodular or diffuse granulomatous infiltrate of lymphocytes, histiocytes and many multinucleated giant cells containing asteroid bodies and elastic tissue (elastic fibre phagocytosis) Usually no necrobiosis and mucin, and less palisading than GA Three zones in well-developed lesions: solar elastosis, granuloma with elastic fibre phagocytosis, and zone of absent elastic fibres)

Answer 41

Epidermis normal, sometimes parakeratosis, hyperkeratosis or acanthosis, such as in the ichthyotic variant Non-caseating (rarely caseating) well-demarcated granulomas in the dermis or subcutaneous tissue, often but not always "Naked" with few lymphoid cells around the epithelioid cells Schauman bodies (round, blue, calcified, laminated inclusions) or asteroid bodies (stellate, intracytoplasmic eosinophilic inclusions) sometimes present within multinucleated giant cells (not specific for sarcoidosis)

Answer 42

Caseating or non-caseating granulomas with foreign material Fibrosis or sclerosis replaces granulomas in older lesions

Answer 43

Epidermis/mucosa normal Interstitial or nodular infiltrate of lymphocytes and plasma cells in an oedematous stroma Tuberculoid granulomas sometimes subtle, not always present, may impinge upon adjacent dilated blood vessels and lymphatics

Answer 44

Nodular infiltrate of large true histiocytes with abundant eosinophilic non-foamy "ground glass" cytoplasm, and positive histiocytic stains Bizarre multinucleated giant cells, often polygonal, with irregular distributed nuclei in older lesions Mixed diffuse infiltrate of lymphocytes, and sometimes neutrophils or eosinophils

Answer 45

Foam cells in dermis (positive for lipid with special stains such as oil-red-O) Touton giant cells (sometimes) Small numbers of lymphocytes or neutrophils in younger lesions (especially eruptive) Fibrosis or cholesterol clefts in older lesions

Answer 46

Nodular or diffuse mixed infiltrate of histiocytes, lymphocytes, and eosinophils (eosinophils more common in younger lesions) Foamy histiocytes and Toulon giant cells in older lesions Fibrosis prominent in older lesions Positive staining with CD68, CD163, HAM56, factor XIIIa (dermal dendrocytes)

Answer 47

Palisading granulomas with areas of necrosis (more severe degeneration than the necrobiosis seen with GA/NLD) Cholesterol clefts common Foamy histiocytes, touton giant cells, foreign body giant cells, lymphocytes, plasma cells, neutrophils

Answer 48

Hyperkeratosis, acanthosis, papillomatosis (verrucous) Foamy histiocytes limited to submucosal or dermal papillae

Answer 49

Subepidermal blister Festooning of dermal papillae Caterpillar bodies (eosinophilic, linear, segmented basement membrane material resembling dyskeratotic cells, sometimes found at the roof of the blister) Sparse hyalinised material around blood vessels Dermal sclerosis in late stage DIF: IgG and C3 around papillary dermal vessels with lesser staining at DEJ in the lamina lucida

Answer 50

Often epidermal atrophy with hyperkeratosis Nodular fissured masses of amorphous eosinophilic material in the superficial dermis Separation between the masses by a thin rim of collagen, elastic tissue, or collarette of epidermal rete ridges Special stains of the eosinophilic material (Congo red and crystal violet) often stain positive as in amyloidosis Solar elastosis common

Answer 51

Hyperkeratosis, papillomatosis (sometimes) Amorphous eosinophilic deposits beginning around the vessels, later diffuse throughout the dermis, with a tendency to be perpendicular to the epidermis and to arrange around adnexal structures and blood vessels Positive staining with colloidal iron, alcian blue, Sudan black, PAS with or without diastase Weak amyloid staining

Answer 52

Deposits of amorphous, eosinophilic, fissured material In systemic: especially around vessels/adnexal structures Special stains positive: crystal violet, Congo red, thioflavin T, pagoda red 9, scarlet red, PAS moderately positive Keratin stains such as EAB-903 may be positive in lichen/macular amyloidosis

Answer 53

Amorphous deposits of eosinophilic material in dermis and subcutaneous tissue with formalin-fixed tissue Brownish, doubly refractive needle-shaped crystals in clefts if alcohol fixed, or in the deeper aspects of incompletely fixed/processed tissue Lymphocytes, histiocytes, and multinucleated giant cells around the deposits Positive staining with von Kossa, but de Galantha is more specific for urates

Answer 54

Large spaces between collagen bundles apparent with H&E Abundant acid mucopolysaccharide between collagen bundles of the dermis: Alcian blue, colloidal iron, or toluidine blue Normal or slightly increased number of fibroblasts Sometimes increased mast cells

Answer 55

Circumscribed deposits of abundant acid mucopolysaccharide between collagen bundles in the superficial dermis, positive with alcian blue, colloidal iron, or toluidine blue stains Fibrosis sometimes Increased mast cells

Answer 56

Hyperplasia of epidermis sometimes Localised increased mucin in clefts between collagen bundles or in a cystic space Not true cyst, but collarette of epidermal rete ridges may clutch the cyst Synovial lining (sometimes) Positive staining with acid mucopolysaccharide stains

Answer 57

Rupture minor salivary duct or gland One or several spaces filled with sialomyucin, lined by granulation tissue or a mixed infiltrate of fibroblasts, lymphocytes, and histiocytes Sialomucin is positive for both neutral mucopolysaccharide (PAS, diastase resistant) and acid mucopolysaccharide

Answer 58

Localised increased dermal mucin Normal or slightly increased number of S100 negative fibroblasts Positive staining with acid mucopolysaccharide stains (Alcian blue, toluidine blue, or colloidal blue)

Answer 59

Dermis markedly thicker than normal, extending below sweat gland coils, with very thick collagen bundles separated by clefts Normal or decrease number of fibroblasts Increase in acid mucopolysaccharide between collagen bundles (stains with Alcian blue, colloidal iron or toluidine blue)

Answer 60

Perivascular and perifollicular lymphocytes Very subtle to moderate amount of mucin between collagen bundles Mucin is positive with acid mucopolysaccharide stains (alcian blue, toluidine blue, sometimes mucicarmine)

Answer 61

Granules within cytoplasm of fibroblasts or histiocytes ("gargoyle cells") and occasionally within keratinocytes that can be stained with Giemsa, toluidine blue, Alcian blue, or colloidal iron Cells may appear vacuolated prior to special stains Special fixation in alcohol may be needed Mucin in middle or deep dermis in papulonodules Hurler's syndrome (MPS I) AR Hunter's syndrome (MPS II) XLR

Answer 62

Dark, basophilic, brittle, often fractured deposits, sometimes surrounded by fibrosis or foreign body reaction Positive staining with von Kossa or alizarin red (more specific for calcium)

Answer 63

Yellow-brown "banana-shaped" deposits on homogenised collagen bundles Small yellow-brown granules in endothelial cells and secretory portion of sweat glands Few multinucleated giant cells (rarely) Positive black staining with methylene blue or cresyl violet

Answer 64

Increased melanin in basal layer Haemosiderin deposits scattered through dermis, mainly around blood vessels and sweat glands (Perl's stain best seen)

Answer 65

Sometimes increased melanin in basal layer Tiny black particles in the dermis, especially around sweat glands, hair follicles, blood vessels, elastic fibres

Answer 66

Fibrosis changes in dermis, sometime more subtle than the impressive clinical findings, often extending into deep subcutaneous tissue Positive staining for CD34 and procollagen-1 (sometimes factor XIIIa positive) Sometimes mucin increased between collagen bundles in dermis (positive for alcian blue or colloidal iron) Usually no inflammation, but in some cases can be present Gadolinium demonstrated in skin lesions with electron microscopy/X-ray spectroscopy

Answer 67

Amorphous, fibrous, or globular basophilic material in the dermis Elastic fibres become bluish-grey and stain positively with elastic tissue stains

Answer 68

Pale, vacuolated, or necrotic keratinocytes Subepidermal blister, or ulceration sometimes Superficial dermal oedema Endothelial proliferation, vascular dilation, thrombi Degeneration of dermal connective tissue

Answer 69

Epidermal hyperplasia, or atrophy, sometimes ulceration Keratinocytes pale, atypical or necrotic Telangiectatic blood vessels, sometimes surrounded by hyper plastic rete ridges Thrombi sometimes Decreased adnexal structures Degenerated dermis (mainly hyalinised, sometimes basophilic) Sometimes atypical, bizarre fibroblasts

Answer 70

Epidermis normal or atrophic Hyalinised dermis and subcutaneous fat, more prominent in late lesions Sparse perivascular lymphocytes, sometimes plasma cells, in dermis or subcutaneous fat, more prominent in early lesions and in morphoea than in systemic sclerosis Decreased adnexal structures, eccrine glands are entrapped by collagen and higher up in the dermis than usual because of increased collagen in subcutaneous fat

Answer 71

Hyalinised dermis, often subtle, requiring fusiform excision adjacent normal skin for comparison to appreciate the dermal atrophy in the involved skin Perivascular lymphocytes in early lesions

Answer 72

Hyperkeratosis (often) but atrophy of spinous layer Follicular plugging Liquefaction degeneration of the basal layer, rare sub-epidermal blister Oedematous homogenised superificial dermis with vascular dilation Lichenoid lymphocytes in early lesions (near basal layer in very early lesions, mid-dermis beneath homogenised zone later) Vascular dilation

Answer 73

Epidermal atrophy Dermal fibrosis of sclerosis Decreased adnexal structures Decreased subcutaneous fat Hutchinson-Gilford (childhood) Werner's syndrome (adult/teen)

Answer 74

Increased dense collagen and increased fibroblasts in the dermis Increased acid mucopolysaccharide between collagen bundles May have normal histology or dermal fibrosis with pilosebaceous hyperplasia

Answer 75

Clumped, calcified elastic fibres in the dermis (positive staining for calcium on alizarin red or von Kossa stains, or for elastic tissue with Verhoeff stain)

Answer 76

Normal appearing skin by light microscopy in most cases Collagen fibres may have subtle thinning, with slight increase in elastic fibres Dermal atrophy may be present Pseudotumors at site of trauma show haemorrhage early, and fibrosis, multinucleated histiocytes and vascular proliferation late

Answer 77

Skin looks normal on H&E Elastic stain shows decreased, thinned, degenerated, or nearly normal elastic fibres in the dermis Lymphocytes, multinucleated giant cells rarely in dermis

Answer 78

Normal epidermis Perivascular lymphocytes, histiocytes, neutrophils, or eosinophils Decreased or completely absent elastic tissue in the dermis with Verhoeff-van Gieson stain, but skin looks nearly normal with H&E

Answer 79

Hyperkeratotic plug containing degenerated material, sometimes associated with follicular orifices, sometimes completely perforating the epidermis or follicle, sometimes with neutrophils or crust Parakeratosis and dyskeratotic keratinocytes Epidermal hyperplasia around the plug No increase in elastic fibres in the dermis and no elastic fibres or collagen fibres within the plug Foreign body giant cells in the dermis at perforation sites (sometimes)

Answer 80

Hyperkeratotic plug with transepidermal elimination of elastic fibres Hyperplastic epidermis that often appears to clutch the dermis at the site of perforation (crab claw/vacuum cleaner) Increased brightly eosinophilic elastic fibres in dermis near perforation (Verhoeff-van Gieson stain) Bramble bush lumpy-bumpy elastic fibres with lateral buds in penicillamine-induced EPS Macrophages, multinucleated giant cells, lymphocytes or neutrophils in the plug or dermis at site of perforation Down syndrome, Ehlers-Danlos syndrome, osteogenesis imperfecta, Marfan syndrome, PXE, Rothmund-Thomson syndrome, acrogeria

Answer 81

Hyperkeratotic plug in the epidermis, often "perforating" through the epidermis Transepidermal elimination of collagen fibres (red with Verhoeff-van Gieson stain) in the plug Macrophages, multinucleated giant cells, lymphocytes, or neutrophils in the plug or dermis at site of perforation

Answer 82

Normal-appearing skin with H&E Mid-dermal loss of elastic fibres seen with Verhoeff-van Gieson stain Macrophages with elastic fibre phagocytosis sometimes

Answer 83

Follicular plugging Sometimes intraepidermal pustules overlying follicles or within follicles Frequently ruptured pilosebaceous apparatus with perifollicular mixed infiltrate of neutrophils, lymphocytes, plasma cells, histiocytes, and/or multinucleated giant cells Sometimes abscesses, sinus tracts, and fibrosis

Answer 84

Perifollicular or intrafollicular mixed infiltrate of lymphocytes, histiocytes, or plasma cells, sometimes resulting in a ruptured follicle surrounded by neutrophils and multinucleated giant cells Causative organisms may be present Perifollicular fibrosis in older lesions

Answer 85

Follicular plugging Perforation of the follicle by degenerating elastic and collagen fibres Perifollicular neutrophils, lymphocytes or plasma cells

Answer 86

Numerous vellus hairs within a follicle

Answer 87

Follicular plugging Sparse perifollicular lymphocytes or neutrophils sometimes

Answer 88

Crystallina: subcorneal vesicles with no inflammatory cells over sweat ducts Rubra: spongiosis of intraepidermal sweat ducts sometimes producing intraepidermal vesicles, perivascular lymphocytes or neutrophils Profunda: red nodules, or pustules, deeper and denser inflammation

Answer 89

Spongiosis or vesicle in plugged follicle near connection with apocrine duct Perivascular or peri-sweat duct lymphocytes or neutrophils Perifollicular foamy histiocytes

Answer 90

Acid mucopolysaccharide deposition (positive with Alcian blue or colloidal iron stains) in hair follicle between keratinocytes, resembling spongiosis Perivascular or lichenoid lymphocytes, histiocytes or eosinophils with exocytosis into the follicles Co-existing MF sometimes

Answer 91

Lymphocytes, sometimes eosinophils, around hair bulb lower portion of follicle in early lesions (swarm of bees) Increased number of miniature (nanogen) telogen or catagen follicles or sometimes early anagen hair follicles in the superficial dermis Fibrous tract remnants (follicular streamers) of destroyed follicles may be present

Answer 92

Lymphocytes mainly around follicles in early lesions Fibrosis and absent follicles in older lesions

Answer 93

Deformed hair shafts and follicles (trichomalacia) Pigmented casts in follicles (blobs of melanin) Empty follicles (hair shafts pulled out), with increased catagen or telogen follicles Perifollicular lymphocytes, plasma cells, or neutrophils usually sparse or absent Perifollicular haemorrhage (sometimes) Perifollicular fibrosis, if follicle is destroyed, a vertical fibrous tract often remains

Answer 94

Miniaturised vellus follicles in late stages Increased telogen hairs in late stages Vertical fibrous stelae of destroyed follicles may be present

Answer 95

Decreased follicles, increased telogen Increased thickness of adipose tissue

Answer 96

Increased telogen hair count No miniaturised follicles

Answer 97

Neutrophils around eccrine sweat glands No bacteria demonstrated Syringosquamous metaplasia may occur in the chemotherapy-induced type

Answer 98

Compact hyperkeratosis Normal or thickened granular layer in most variants (except ichthyosis vulgaris/acquired) Varying degree of acanthosis, usually not much parakeratosis

Answer 99

Compact orthokeratosis and acanthosis Decreased or absent granular layer Follicular plugging (sometimes)

Answer 100

Compact orthokeratosis and acanthosis Hypergranulosis Epidermolytic degeneration of keratinocytes Intraepidermal blisters

Answer 101

Decreased number and hypoplasia of sebaceous glands and hair follicles Decreased number or absent sweat glands in patients with anhidrotic form

Answer 102

Hyperkeratosis, parakeratosis sometimes, pseudoepitheliomatous hyperplasia sometimes, basaloid hyperplasia sometimes Follicular plugging sometimes Papillomatosis and acanthosis Acantholytic dyskeratotic keratinocytes often forming corps roads and grains Clefts or lacunae in suprabasal location due to acantholysis

Answer 103

Epidermis normal or atrophic Melanin incontinence Absent or minimal interface lymphocytes

Answer 104

Epidermal atrophy Liquefaction degeneration of the basal layer in early lesions Melanin incontinence Perivascular or lichenoid lymphocytes in early lesions Dilated blood vessels RECQL4 (DNA Helicase gene)

Answer 105

First stage: eosinophilic spongiosis and intraepidermal vesicles containing eosinophils Dyskeratotic keratinocytes Perivascular lymphocytes and eosinophils Second stage: Papillomatosis, hyperkeratosis and acanthosis Pale glassy keratinocytes, often dyskeratotic, and forming squamous eddies Minimal perivascular lymphocytes Melanin incontinence IKBKG (of NEMO complex) Third stage: melanin incontinence with basal cell degeneration or basal cell hyperpigmentation

Answer 106

Decreased melanocyte and melanin at the basal layer

Answer 107

Severe dermal atrophy so that the subcutaneous fat may reach the epidermis PORCN gene

Answer 108

Melanocytes are present at the basal layer but do not actively produce melanin Decreased or absent melanin demonstrated with Fontana melanin stain Electron microscopy may detect immature or decreased melanosomes

Answer 109

Interface dermatitis or perisvascular lymphocytic dermatitis Telangiectasia RECQ protein-like 3

Answer 110

Epidermis may be atrophic or hyperkeratotic Necrotic keratinocytes sometimes Solar elastosis, telangiectasia Basal layer decreased or increased melanin, dermal melanin incontinence Perivascular lymphocytes

Answer 111

Dilated blood vessels in the dermis Cafe-au-lait macules (sometimes)

Answer 112

Subcorneal pustule filled with neutrophils and sometimes occasional acantholytic cells Spongiosis often Dermal perivascular lymphocytes and neutrophils Gram-positive cocci sometimes found in pustule (culture more helpful) *Staphylococcus aureus and/or streptococcus pyogenes*

Answer 113

Subcorneal blister containing only rarely inflammatory cells, and sometimes some acantholytic cells Minimal or absent perisvascular neutrophils and lymphocytes Bacteria not present in the blistering toxin-induced lesions ``` *Staphylococcus aureus (SSSS, TSS) Streptococcus pyogenes (Scarlet fever, rheumatic fever, TSS) Salmonelli typhi (Typhoid)* ```

Answer 114

Epidermis normal, sometimes with necrosis Dermal oedema Diffuse or interstitial infiltrate of predominantly neutrophils in the dermis (sometimes sparse) Bacteria uncommonly can be seen with Gram stain Culture of biopsy positive in less than 10% of cases *Streptococcus pyogenes, staphylococcus aureus, others*

Answer 115

Epidermal necrosis or ulceration Dermal oedema Extravasated erythrocytes Diffuse dermal neutrophils or minimal inflammation Large gram-positive rods (1-8 microns) often visible with H&E *Bacillus anthracis*

Answer 116

Epidermal necrosis or ulceration Mixed diffuse infiltrate of neutrophils, lymphocytes, histiocytes, and multinucleated giant cells Granulomas may be tuberculoid or sarcoidal, sometimes with caseation Gram-negative coccobacilli usually cannot be identified with special stains (Dieterle silver stain or fluorescent antibody stains may be helpful) *Frascisella Tularensis*

Answer 117

Three zones of inflammation under an ulceration (not as specific as once thought) Necrotic debris, fibrin, and neutrophils on the surface Granulation tissue in the middle zone Lymphocytes, plasma cells deep Gram-negative coccobacilli can rarely be demonstrated on Gram or Giemsa stains (best seen on smears) *Haemophilus ducreyi*

Answer 118

Ulceration with granulation tissue Pseudoepitheliomatous hyperplasia at the ulcer border (sometimes) 1.2 micron Gram-negative organisms (Donovan bodies) sometimes within histiocytes with Giemsa or Warthin-Starry stains (best seen on smears) *Klebsiella granulomatis*

Answer 119

Pseudoepitheliomatous hyperplasia sometimes in older lesions Dense diffuse infiltrate of many plasma cells, Russell bodies, histiocytes, neutrophils and lymphocytes Gram-negative rods (2-3 microns) seen within large vacuolated histiocytes (Mikulicz cells) with H&E stain, or better with Giemsa, PAS, Warthin-Starry, or immunostains Marked fibrosis in older lesions *Klebsiella rhinoscleromatis*

Answer 120

Epidermis hyperplastic or ulcerated, sometimes with neutrophilic microabscesses Diffuse dermal mixed infiltrate of neutrophils, histiocytes, and plasma cells Tuberculoid granulomas often present, usually without caseation Acid-fast bacilli found by AFB stain, culture, PCR Prominent fibrosis sometimes *Tuberculosis, leprae Marinum, ulcerans, avium-intracellulare (AIDS) Rapid growers: fortuitum, abscessus, chelonae*

Answer 121

Diffuse infiltrate of predominantly foamy histiocytes, separated from the epidermis by a Grenz zone Acid-fast bacilli seen with Fite stain, sometime in clumps called globi

Answer 122

Tuberculoid granulomas that may reach the epidermis (no Grenz zone), with a tendency to be linear along cutaneous nerves and usually without caseation Acid-fast bacilli rare, or not present with Fite stain *Mycobacterium leprae / lepromatosis*

Answer 123

Ulceration of the epidermis Diffuse infiltrate of many plasma cells, lymphocytes, histiocytes Endothelial swelling and proliferation Spirochetes often present with Within-Starry stain / or T. palladium immunostain *Treponema pallidum*

Answer 124

Epidermis may be normal, hyperkeratotic, psoriasiform, necrotic or ulcerated Neutrophils or pustules may be in the epidermis Perivascular or lichenoid infiltrate of many plasma cells, lymphocytes, and histiocytes. Eosinophils occasionally present Granulomatous infiltrate may be present in older lesions Endothelial swelling and proliferation Spirochetes present in epidermis or dermis in one-third of cases, best seen as epitheliotropic or vasculotropic on immunostain *Treponema pallidum*

Answer 125

Epidermis normal, atrophic, hyperplastic, or ulcerated Tuberculoid granulomas with or without caseation often with plasma cells Endothelial swelling and proliferation Spirochetes usually not identified with Warthin-Starry stain Fibrosis in some lesions

Answer 126

Sometime spongiosis Perivascular lymphocytes and plasma cells or eosinophils Spirochetes with silver stains (rarely found) or with molecular biologic techniques *Borrelia burgdorferi*

Answer 127

Epidermal atrophy Periavascular or lichenoid lymphocytes, plasma cells, or eosinophils in early lesions Dermal oedema in early lesions, severe dermal atrophy or sclerosis later Decreased or absent adnexa in older lesions *Borrelia burgdorferi*

Answer 128

Perivascular or lichenoid infiltrate with lymphocytes, plasma cells, neutrophils or eosinophils, sometimes forming palisading granulomas ## Footnote *Bartonella henselae*

Answer 129

Pustules and epidermal necrosis, often Septic neutrophilic vasculitis Extravasated erythrocytes and thrombi Gram-negative diplococci seldom demonstrated *Neisseria gonorrhoeae*

Answer 130

Pustules and epidermal necrosis sometimes Septic neutrophilic vasculitis, with more lymphocytes in the chronic form Extravasated erythrocytes and thrombi Gram-negative diplococci seldom demonstrated *Neisseria meningitidis*

Answer 131

Epidermal necrosis or ulceration Dermal necrosis or infarction Sparse inflammation with lymphocytes or neutrophils Numerous gram-negative bacilli in dermis stain poorly with H&E Vasculitis and thrombi common *Pseudomonas aeruginosa*

Answer 132

Diffuse infiltrate of granular von Hansemann histiocytes containing Michaelis-Gutmann bodies (5-15 micron granules that stain positive with PAS, von Kossa and Perl's stain) Diffuse neutrophils, plasma cells or lymphocytes may be present *Escherichia coli*

Answer 133

Neutrophils sometimes in the stratum corneum, parakeratosis often Compact orthokeratosis rather than normal basket-weave pattern Sandwich sign (orthokeratosis or parakeratosis alternated in layers with basket-weave stratum corneum, often a clue for the presence of hyphae) Spongiosis or intraepidermal vesicles (sometimes) Psoriasiform epidermis (sometimes) Folliculitis (sometimes) Variable inflammatory response: may appear normal, or perivascular or diffuse mixed infiltrate of lymphocytes, histiocytes, neutrophils, or eosinophils Fungal hyphae (2-4 microns in diameer) in stratum corneum or in follicles - best seen with PAS or GMS stains

Answer 134

Normal-appearing skin without inflammation or with minimal perivascular lymphocytes Short hyphae and budding yeast from 2-4 microns in stratum corneum or in follicles Easier to see in H&E compared to dermatophytes, but are best seen with PAS or GMS stains

Answer 135

Skin may look normal with H&E stain at scanning magnification Brown septate hyphae in stratum corneum can be seen with H&E stain

Answer 136

Neutrophils, parakeratosis, and crusting common in stratum corneum Pseudohyphae and budding yeast in the stratum corneum (3-7 microns) which can sometimes be seen with H&E, but are more easily seen with PAS or GMS stains Perivascular lymphocytes and neutrophils in the dermis

Answer 137

Epidermis unremarkable Budding yeast (5-20 microns) are numerous in the dermis, staining faintly with H&E or better with GMS Prominent capsule around organisms that does not stain with H&E giving the dermis a vacuolated gelatinous appearance Capsule contains mucin Very little inflammatory response *Cryptococcis neoformans*

Answer 138

Often ulcerated with pseudoepitheliomatous hyperplasia Yeasts are small (2-10 microns) and less numerous: free in tissue or within histiocytes/giant cells Dense mixed dermal granulomatous infiltrate of many neutrophils, histiocytes, giant cells and plasma cells *Cryptococcus neoformans*

Answer 139

Pseudoepitheliomatous hyperplasia in older lesions, sometimes intraepidermal neutrophilic microabscesses Diffuse suppurative granulomatous dermal infiltrate of neutrophils, lymphocytes, histiocytes, plasma cells (and multinucleated giant cells in older lesions), and often many eosinophils. Sometimes caseation Large thick-walled spores measuring 10–80 microns with a granular cytoplasm or containing 2–10-micron endospores. Often visible with H&E, but best seen with PAS or GMS stains *Coccidioides immitis/posadasii*

Answer 140

Pseudoepitheliomatous hyperplasia, sometimes intraepidermal neutrophilic microabscesses Diffuse mixed dermal infiltrate of neutrophils (often abscesses), lymphocytes, histiocytes, plasma cells and multinucleated giant cells Spores 5-20 microns Organisms up to 60 microns with multiple nods (marine pilot's wheel) *Paracoccidioides brasiliensis*

Answer 141

Pseudoepitheliomatous hyperplasia, sometimes intraepidermal neutrophilic microabscesses Diffuse mixed infiltrate of neutrophils (often abscesses), lymphocytes, histiocytes, plasma cells, and multinucleated giant cells; no caseation Thick-walled spores 8–15 microns, sometimes with a characteristic broad-based bud, either within giant cells or free in the tissue. Often visible with H&E, but seen best with PAS or GMS stains *Blastomyces dermatitidis*

Answer 142

Epidermis or mucosa often ulcerated Diffuse mixed dermal infiltrate of neutrophils, lymphocytes, histiocytes, and a few giant cells, necrosis common Sparse leukocytoclastic vasculitis infiltrate in some patients with AIDS instead of the diffuse infiltrate Numerous small 2-4 micron spores surrounding by a clear space can be seen within histiocytes and giant cells with H&E stains Seen more readily with PAS, GMS, Giemsa, Gram stains *Histoplasma capsulatum*

Answer 143

Pseudoepitheliomatous hyperplasia; sometimes intraepidermal neutrophilic microabscesses Diffuse mixed dermal infiltrate of neutrophils (often abscesses), lymphocytes, histiocytes, plasma cells, and multinucleated giant cells; no caseation Clusters or chains of brown spores (Medlar bodies, “copper pennies”) of 6–12 microns within histiocytes in microabscesses, as well as free within the tissue. Spores reproduce by fission instead of budding *Phialophora, Fonsecaea, and Cladosporium*

Answer 144

Pseudoepitheliomatous hyperplasia; often with intraepidermal neutrophilic microabscesses or ulceration Diffuse mixed dermal infiltrate of neutrophils (often abscesses), histiocytes, plasma cells, and multinucleated giant cells Round, oval, or cigar-shaped spores range of 3–8 microns but are often difficult to find, even with PAS and GMS stains Rarely, eosinophilic star-like deposits around the yeast (asteroid bodies), not to be confused with the intracytoplasmic asteroid bodies sometimes seen with sarcoidosis *Sporotrichum schenckii*

Answer 145

Epidermis often ulcerated Granulation tissue, thrombi, necrosis Sparse inflammation in many cases, or neutrophilic abscesses may be present Non-septate (coenocytic), large hyphae (diameter up to 30 microns) with right-angled branching are seen with H&E, but are best seen with PAS or GMS stains *Rhizopus, Mucor, or Absidia*

Answer 146

Diffuse mixed dermal infiltrate of neutrophils, lymphocytes, histiocytes, or multinucleated giant cells. Often a predominance of dermal necrosis with very little inflammation Septate hyphae with branching at acute angles in dermis and often in blood vessels Aspergillus immunostain available

Answer 147

Abscesses of neutrophils, mixed infiltrate, granulomatous inflammation, and/or granulation tissue, with fibrosis in older lesions Granules (sclerotia) large colonies of organisms usually 0.5mm-3mm, large enough to see grossly Bacteria granules (sulfur granules) whitish/yellowish \<1 micron thick Fungi granules (brown or black) with thicker hyphae at 5 microns *Actino: Nocardia, Actinomadura, Streptomyces Eu: Pseudoallescheria boydiii, Aspergillus, Curvularia, Madurella*

Answer 148

Polypod lesions of granulation tissue with mixed inflammatory infiltrate Characteristic numerous huge sporangia (up to 500 microns) containing endospores *Rhinosporidium seeberi*

Answer 149

Granulomatous inflammation with multinucleated giant cells, plasma cells, and lymphocytes Prominent fibrosis Spores are uniform in size (6-12 microns), easily seen with H&E, and form a string of pearls chain *Lacazia loboi*

Answer 150

Brown hyphae (dematiacious hyphae) found in the dermis or subcutaneous tissue Variable mixed inflammatory reaction, suppurative granulomatous often, fibrosis often Walled-off cystic space (pheomycotic cyst) sometimes Foreign body may be present *Alternaria, Bipolaris, Curvularia, Exophiala, Exserohilum, and Phialophora*

Answer 151

Necrosis often prominent Inflammation may be sparse, or suppurative, and granulomatous Non-pigmented hyalinised septate hyphae often visible with H&E, better seen with PAS or GMS stains (non-pigmnted septate hyphae) *Acremonium, fusarium, penicillium*

Answer 152

Diffuse suppurative granulomatous inflammation Necrosis prominent with sparse inflammation in patients with poor immunity Yeast with diameter of 3 microns in histiocytes, up to 8 microns when extracellular, dividing by binary fission without buds, appearing elongated and septate Positive staining of yeast with PAS and GMS but not with mucicarmine

Answer 153

Hyperkeratosis, papillomatosis, hypergranulosis Columns of parakeratosis especially over projecting dermal papillae V acuolated superficial keratinocytes with pyknotic raisin-like nuclei (koilocytes) Rete ridges often slow inward at borders of lesion (arborisation, toeing inward) Dilated capillaries in dermal papillae Perivascular lymphocytes

Answer 154

HSV and VZV can not be distinguished with routine H&E staining Intraepidermal vesicle or ulceration may not be present in early lesions Epidermal necrosis and ballooning degeneration: herpetic cytopathic changes are enlarged and pale keratinocytes, with steel-gray nuclei, margination of chromatin at the edge of the nucleus, sometimes with pink intranuclear inclusions surrounded by an artifactual cleft, acantholysis or multinucleated keratinocyte formation Extravasated erythrocytes often Perivascular and diffuse lymphocytes or neutrophils, sometimes with changes of leukocytoclastic vasculitis

Answer 155

Intraepidermal vesicles with few balloon cells (usually not multinucleated) and inclusion bodies that are primarily intracytoplasmic (Guarnieri bodies) Mixed diffuse dermal infiltrate of lymphocytes and neutrophils

Answer 156

Epidermal hyperplasia producing a crater filled with molluscum bodies (Henderson-Patterson bodies) that are huge, up to 35 microns, eosinophilic to basophilic intracytoplasmic inclusions that push the nucleus and numerous keratohyaline granules aside Intact lesions show little or no inflammation, while ruptured lesions exhibit dense mixed inflammatory response consisting of mononuclear cells, neutrophils, and multinucleated giant cells Rarely, CD30+ atypical reactive lymphocytes resemble lymphoma

Answer 157

Vacuolated superficial epidermis with inclusion bodies that are predominantly intracytoplasmic, occasionally intranuclear Epidermal necrosis, often with extremely delicate finger-like projections into the dermis Dense, diffuse, mixed inflammatory infiltrate in the dermis Dermal oedema, extravasated erythrocytes, dilated blood vessels

Answer 158

Intraepidermal multiloculated vesicles or pustules Epidermal necrosis, or ballooning degeneration without inclusion bodies or multinucleated keratinocytes Papillary dermal oedema, sometimes resulting in subepidermal blisters Perivascular lymphocytes or neutrophils

Answer 159

Epidermis normal or with focal parakeratosis or focal spongiosis Mild ballooning degeneration or multinucleated keratinocytes rarely (not as prominent as seen with herpes viruses) or focal keratinocyte necrosis Perivascular or interface lymphocytes

Answer 160

Epidermis normal, verrucous or ulcerated Vascular dilation with large cytomegalic endothelial cells Intranuclear and intracytoplasmic inclusion bodies (owl eye appearance) Variable lymphocytes or neutrophils Positive CMV immunostain Viral particles indistinguishable from other herpes viruses by electron microscopy

Answer 161

Non-specific perivascular lymphocytes (not neutrophils) in biopsies from the rash

Answer 162

Focal parakeratosis, sometimes crusting Focal spongiosis, acanthosis, dyskeratosis Papillary dermal oedema often Perivascular lymphocytes, rare eosinophils Extravasated red blood cells sometimes

Answer 163

Epidermal necrosis, or spongiosis at initial bite site Dermal oedema, or subepidermal blister in rickettsialpox, which may appear to be intraepidermal after re-epithelialisation Vasculitis with predominance of lymphocytes and histiocytes, although some cases are neutrophilic Extravasated erythrocytes and thrombi often Organisms are difficult to demonstrate by special stains such as Giemsa, but direct immunofluorescence and immunoenzyme antibodies demonstrating the organisms in frozen sections are available

Answer 164

Epidermis normal or ulcerated Diffuse mixed infiltrate of neutrophils, lymphocytes, histiocytes, plasma cells and sometimes multinucleated giant cells Stellate abscesses often in lymph nodes, later becoming granulomatous Organisms rarely demonstrated with Giemsa stain in histiocytes *Chlamydia trachomatis (L1-L3)*

Answer 165

Epidermis normal, atrophic, hyperplastic or ulcerated Diffuse mixed granulomatous dermal infiltrate of lymphocytes, histiocytes, plasma cells, neutrophils, and multinucleated giant cells, occasional caseation necrosis Fibrosis in older lesions Amastigote organisms are usually present within histiocytes 2-3 microns, 1-micron round nucleus (H&E or Giemsa or Tzanck smear)

Answer 166

Epidermis ulcerated or hyperplastic Mixed diffuse infiltrate of neutrophils, lymphocytes, histiocytes and multinucleated giant cells Dermal necrosis common Organisms usually visible with H&E but highlighted with PAS, GMS, acid mucopolysaccharide stains 2-11 microns in size Can look like soccer balls *Prototheca spp*

Answer 167

Larva (cysticercus, 6-18mm long), secretory tegument surrounded by a unilocular cystic cavity and fibrosis in subcutaneous tissue, usually in subcutaneous or deeper soft tissue, often pale and necrotic Scolex (mouth), is important to find on deeper levels, with sucking grooves known as bothria Calcareous bodies (oval calcified focal concretions) Very little inflammation until larva dies: mixed inflammatory infiltrate with sometimes calcification *Taenia solium*

Answer 168

Tightly-coiled solitary worm with a thick cuticle, considerable muscle, and diameter of 125-250 microns, usually in subcutaneous tissues Mixed inflammatory infiltrate with lymphocytes, histiocytes, plasma cells, eosinophils, multinucleated giant cells

Answer 169

Onchocercoma: adult worms (100-500microns in diameter) live in orgies within nodules in the subcutaneous tissue, surrounded by dense fibrosis, or multinucleated giant cells. Female worms have paired uteri Dermatitis: microfilariae (5-9 microns) are found within adult female worms or migrating freely in the dermis

Answer 170

Scale, crust, spongiosis, or intraepidermal vesicle containing eosinophils Dermal oedema Perivascular lymphocytes, histiocytes, and many eosinophils Larva (about 0.5mm thick and up to 10mm long) difficult to find, usually in deeper epidermis

Answer 171

Epidermis may have scale crust, epidermal necrosis, or epidermal hyperplasia Spongiosis or intraepidermal vesicle (often) Dermal oedema, sometimes subepidermal vesicle Perivascular (usually superficial and deep) neutrophils, lymphocytes (sometimes atypical or CD30+), or eosinophils, older lesions show diffuse or nodular inflammation similar to lymphocytoma cutis Endothelial swelling (often)

Answer 172

Folliculorum within hair follicles (100-400microns) Brevis within sebaceous glands Variable inflammatory reaction Lymphocytes in the pilosebaceous unit, sometimes suppurative or granulomatous inflammation

Answer 173

Eggs or mites (200-400 microns) or scybala (brown faces) are present in the sub corneal zone Sometimes spongiosis or epidermal hyperplasia Perivascular or moderately diffuse dermal lymphocytes and eosinophils

Answer 174

Maggots found in dermis or subcutaneous tissue with characteristics depending upon the species, many have thick corrugated skeletal wall Dermatobia hominis is a more commonly encountered maggot in South America Diffuse mixed infiltrate of lymphocytes, histiocytes, and eosinophils

Answer 175

Hyperkeratosis, acanthosis, crusting Female flea beneath stratum corneum may reach 5mm in diameter when becomes swollen with eggs Skeletal muscle and red hollow tubules present Mixed inflammatory infiltrate, sometimes abscess formation

Answer 176

Foamy stroma with H&E stain Round, no-budding 5-10 micron cysts (teacup in saucer appearance) in the dermis or subcutaneous tissue are best stained with GMS

Answer 177

Ulceration or pseudoepitheliomatous hyperplasia Granulation tissue, dermal oedema, necrosis, fibrosis Mixed diffuse inflammation, may be granulomatous Trophozoites resembling epithelioid histiocytes, 15-40 microns, with a bubbly or granular cytoplasm and single nuclear that has marginated chromatin may be seen with H&E, but are more easily seen with PAS Erythrophagocytosis by trophozoites (sometimes) Some species can be cultured or PCR/IF

Answer 178

Ulceration or epithelial hyperplasia Mixed inflammation: histiocytes, plasma cells, lymphocytes Trypanosomes have a nucleus and kinetoplast that is Giemsa stain positive

Answer 179

Pseudoepitheliomatous hyperplasia or epidermal necrosis (sometimes) Perivascular or interface lymphocytes and macrophages Dermal necrosis and extravasated erythrocytes (sometimes) Trophozoites (2-8 microns) or cysts (8-30 microns), containing numerous smaller bradyzoites are found in macrophages or free in the dermis in half of the cases, some forms are PAS positive Immunostains, serology and PCR detection is available

Answer 180

Granulomas and neutrophils around eggs (up to 120 microns long, some are PAS or AFB stain positive) Egg spine positions determine species / geographic origin too Adult worms rarely seen in blood vessels

Answer 181

Septal panniculitis of lymphocytes, histiocytes, neutrophils and/or eosinophils Multinucleated giant cells in older lesions without caseation Septal fibrosis in older lesions Mild fat necrosis sometimes with foamy histiocytes

Answer 182

Lobular panniculitis with neutrophils, lymphocytes (sometimes mixed with a septal pattern) Fat necrosis with foamy macrophages Cystic spaces may occur in dissolved fat lobules Necrosis and inflammation may spill over in the dermis, resulting in necrosis draining through ulcers Fibrosis in late lesions

Answer 183

Lobular panniculitis of neutrophils, lymphocytes, and histiocytes Cystic spaces in subcutaneous fat due to ruptured fat cells

Answer 184

Needle-shaped clefts within fat cells and foamy histiocytes Mild fat necrosis surrounded by sparse or absent granulomatous infiltrate of lymphocytes, histiocytes and multinucleated giant cells Prominent sclerosis or fibrosis

Answer 185

Needle-shaped clefts within fat cells, and foamy histiocytes Fat necrosis and granulomatous infiltrate of lymphocytes, histiocytes and multinucleated giant cells Calcification common

Answer 186

Ulceration sometimes Lobular granulomatous panniculitis with mixed infiltrate of lymphocytes, histiocytes, plasma cells and multinucleated giant cells Caseation necrosis sometimes Vasculitis in the fat often involving arteries or small veins Fibrosis in older lesions

Answer 187

Mixed infiltrate of neutrophils, lymphocytes, histiocytes, or multinucleated giant cells within and surrounding a vein in the deep dermis or subcutaneous fat Thrombosis frequent

Answer 188

Mixed lobular panniculitis with lymphocytes, foamy histiocytes, and multinucleated giant cells Fat necrosis with "ghost-like" fat cells and basophilic deposits of calcium salts of fatty acids

Answer 189

Epidermal or dermal changes similar to stasis dermatitis Fat necrosis, sclerosis, foamy macrophages, lymphocytes, in a diffuse or lobular pattern

Answer 190

Early lesions may show the inflammatory patter in the fat, fat necrosis with foam lipophages, plasma cells and lymphocytes with relatively normal lipocytes and blood vessels Other early lesions may show the involution pattern in the fat: small lipocytes, hyalinisation, myxoid changes, increased number of small blood vessels Late lesions have a profound decrease or absence of fat

Answer 191

Scale crust often, with confluent parakeratosis, fibrin and neutrophils in the stratum corneum. Sometimes bacteria and candida Hypogranulosis Psoriasiform hyperplasia, spongiosis, sometimes intraepidermal vesicles Pale, or dyskeratotic epidermis Perivascular lymphocytes

Answer 192

Decreased or absent melanin and melanocytes in basal layer in well-developed lesions (often difficult to appreciate with H&E staining, and require special stains) Hyperkeratosis and acanthosis can sometimes develop to compensate for loss of pigment Perivascular lymphocytes only in early lesions

Answer 193

Epidermal atrophy (sometimes) Mild spongiosis (sometimes) Grade 1: liquefaction degeneration (vacuolar alteration) of the basal layer Grade 2: dyskeratotic or necrotic keratinocytes, sometimes with adjacent lymphocytes (satellite cell necrosis), sparse perivascular or interface dermatitis, melanin incontinence (sometimes) Grade 3: sub-epidermal microvesicle Grade 4: frank subepidermal blister, complete epidermal necrosis in severe cases

Answer 194

Epidermal atrophy with superficial or deep ulcer Dermal atrophy, fibrosis with absent adnexa Lymphocytes and neutrophils associated with ulcer

Answer 195

Variable histology depending upon the type of lesion Spongiosis or intraepidermal vesicles sometimes Necrotic keratinocytes sometimes Usually no liquefaction degeneration of the basal layer Superficial dermal oedema or subepidermal vesicle sometimes Superficial and deep perivascular or nodular lymphocytes, usually spares follicles Negative DIF for immunoglobulin and complement deposition

Answer 196

Hyperkeratosis (sometimes) Follicular plugging Epidermal atrophy or hyperplasia Colloid bodies sometimes in basilar epidermis or papillary dermis Liquefaction degeneration of the basal layer Melanin incontinence Thickened basement membrane Increased mucin in dermis Perivascular and periadnexal, sometimes lichenoid, lymphocytes with occasional plasma cells, but almost always no eosinophils Immunofluorescence reveals granular deposits of IgM, IgG and complement at DEJ - positive staining both lesional and normal skin indicated SLE

Answer 197

Usually more subtle than lupus erythematosus Epidermis atrophic or normal Liquefaction degeneration of basal layer Thickened basement membrane (sometimes) Dermal oedema Dermal mucin Sparse perivascular or interface lymphocytes Sometimes dermal or subcutaneous calcifications DIF usually negative

Answer 198

Perichondrial inflammation (neutrophils, lymphocytes, or plasma cells) Degeneration of cartilage with loss of chondroitin sulphate (decreased basophilia) and vacuolisation of chrondrocytes Perichondrial fibrosis in older lesions

Answer 199

Hyperplasia of epidermis, often with focal ulceration Granulation tissue, fibrosis, solar elastosis and mixed inflammatory infiltrate (lymphocytes, neutrophils, plasma cells) between ulcer and underlying cartilage Degeneration of cartilage, often with blending with fibrosis, sometimes with transepidermal elimination

Answer 200

Hyperkeratosis, papillomatosis, acanthosis, sometimes hypergranulosis Epidermolytic hyperkeratosis (rarely) Acantholytic dyskeratosis (rarely) Perivascular lymphocytes (often)

Answer 201

Epidermal proliferation (variable combinations of hyperkeratosis, papillomatosis, acanthosis) Keratinocytes often appear basaloid Horn pseudocysts (often) Abundant melanin in basal layer or throughout epidermis Sharp demarcation (string sign) of base of epidermal proliferation

Answer 202

Orthokeratosis, hypergranulosis, acanthosis Papillomatosis, often resembling church spires

Answer 203

Cornoid lamella: column of parakerotosis under which there is hypogranulosis and keratinocytes with dyskeratosis or pale staining Epidermis in central part of lesion may be normal, hyperplastic, or atrophic Perivascular or lichenoid lymphocytes, sometimes localised beneath cornoid lamella

Answer 204

Hyperkeratosis, papillomatosis Acanthosis minimal/or absent (misnomer) Basal layer hyperpigmentation (often)

Answer 205

Scale-crust on surface of epidermis (often) Neutrophils in epidermis, often with microabscesses in stratum corneum Psoriasiform proliferation of pale (clear) keratinocytes, with sharp demarcation from normal epidermis Perivascular lymphocytes Dilated blood vessels in oedematous pale dermal papillae

Answer 206

Comedo-like invagination of epidermis filled with hyperkeratosis, parakeratosis, acantholytic, dyskeratotic keratinocytes (corps ronds/grains) Dermal papillae lined by basal cells may project up into the invagination resembling villi

Answer 207

Hyperkeratosis (often), ulceration (sometimes) Parakeratosis, especially overlying atypical keratinocytes often sparing epidermis over adnexa (alternating pink and blue hue in corneum: flag sign) Atypical keratinocytes, (sometimes subtle), with loss of orderly keratinocyte maturation, hyperchromatism, pleomorphism, increased mitoses, dyskeratosis, sparing epidermis above adnexa, too many buds into the papillary dermis Perivascular or lichenoid lymphocytes, sometimes plasma cells Solar elastosis in the dermis

Answer 208

Hyperkeratosis, acanthosis Cytologic atypic of keratinocytes often, may represent SCCIS Variable perivascular lymphocytes in dermis

Answer 209

Parakeratosis, hyperkeratosis, acanthosis Atypical keratinocytes with hyperchromatism, pleomorphism, increased atypical mitoses, dyskeratosis, loss of orderly maturation through the epidermis. Full thickness atypic Clear cells or pagetoid cells can be prominent in some cases Perivascular or lichenoid infiltrate of lymphocytes or plasma cells

Answer 210

Invasion of dermis by atypical keratinocytes (hyper chromatic, pleomorphic cells, often epithelioid, with atypical mitoses) Squamous eddies or keratin pearls (sometimes) Variable perivascular, lichenoid or diffuse lymphocytes or plasma cells Perineural invasion in some aggressive forms (more common than in BCC)

Answer 211

Keratin-filled crater Pale, eosinophilic glassy, well-differentiated epithelial proliferation, often with lips extending over both sides of crater, often with squamous eddies or keratin pearls Sometimes microabscesses of neutrophils within the epithelium Cytologic atypic of keratinocytes no more than mild Elastic fibres sometimes found within epithelium of base of lesion Perivascular or lichenoid infiltrate of lymphocytes, sometimes with eosinophils or plasma cells

Answer 212

Pale staining Paget's cells often with atypical nuclei scattered through the epidermis Groups of them may compress and flatten basal cells, appearing like the eyeliner sign found sometimes in Bowen disease May appear multifocal with skip areas Usually no dyskeratosis, unlike Bowen disease Paget cells usually positive for CEA, EMA, androgen receptor, keratin 8 (low molecular weight), or cam5.2, or CK7, PAS with or without diastase, alcian blue, mucicarmine CK20 commonly associated with perianal cases Gross cystic disease fluid protein often positive (less common with internal malignancy) Underlying adenocarcinoma sometimes seen within dermis

Answer 213

Ulceration of epidermis sometimes Basaloid tumour cells budding from epidermis or follicles or within the dermis with variable atypia Retraction artifact, stroma separates from tumour lobules, often but often absent on frozen sections Peripheral palisading of nuclei (often) Mucin in the stroma or with basaloid aggregates (often) Solar elastosis in the dermis Perineural invasion in some aggressive forms Variable infiltrate of lymphocytes, plasma cells, rarely lymphoid follicles around the tumour

Answer 214

Fibroepithelial digitations with bland epithelial strands or solid aggregates with invaginated fibrous stroma, sometimes giving the appearance of Swiss cheese holes in the epithelial aggregates

Answer 215

Cyst contains lamellated keratin Cyst lined by squamous epithelium, sometimes flattened, with a granular layer

Answer 216

Cyst contains amorphous, dense and compact, homogenized keratin Cyst lined by squamous epithelium The keratinocytes are often pale, and there is no granular layer Calcification common within the cyst

Answer 217

Cyst contains lamellated keratin and often hair shafts Cyst lined by by squamous epithelium with a granular layer Multiple hair follicles open into the cyst, sometimes with sebaceous glands or sweat glands

Answer 218

Cyst is small and contains lamellated keratin and vellus hair shafts Cyst lined by squamous epithelium with a granular layer Hair follicles sometimes attached to cyst

Answer 219

Cyst may contain sparse keratin or hair shafts, but frequently appears empty because the oily sebaceous fluid dissolves during processing Cyst wall consists of ruggated squamous epithelium with a wrinkled crenulated (wavy or serrate outline) eosinophilic refractile cuticle of keratin instead of a granular layer, often resembling shark’s teeth. Sebaceous glands within or adjacent to the cyst wall, opening into the cyst

Answer 220

Cyst is often multilocular and appears empty because fluid washes out during processing Cyst wall varies from cuboidal, ciliated, and non-ciliated columnar to squamous epithelium Thymic tissue (aggreagates of immature and mature lymphocytes) with Hassall's corpuscles (concentrically hyalinised collection of degenerating cells of 20-50 microns, sometimes calcified) Cholesterol clefts, granulomatous inflammation common

Answer 221

Cyst usually appears empty because fluid runs out after biopsy Cyst lining consists of cuboidal or columnar ciliated epithelium, without goblet (mucin-secreting) cells

Answer 222

Cyst contains keratin or mucin Cyst lining varies from pseudostratified columnar (with or without goblet cells or cilia) to squamous epithelium. No smooth muscle, mucous glands, or cartilage adjacent to lining Thyroid follicles or lymphoid follicles may be present

Answer 223

Cyst contains laminated keratin Sinus tract or cyst lined by squamous epithelium with a granular layer, or by columnar epithelium with or without cilia or goblet (mucus-secreting) cells Cysts often surrounded by lymphoid follicles

Answer 224

Cyst contains keratin or mucin Cyst lining varies from pseudostratified columnar (with or without goblet cells or cilia) to squamous epithelium Lining may be surrounded by mucous glands, smooth muscle, lymphoid follicles, or cartilage

Answer 225

Cyst appears empty because fluid leaks out Cyst lined by thin cuboidal or columnar epithelium (often two layers of cells)

Answer 226

Cyst appears empty because fluid leaks out after biopsy Cyst lined by pseudostratified columnar epithelium

Answer 227

Intracartilaginous cystic space with degenerated cartilage and amorphous eosinophilic material Fibrosis, granulation tissue or granulomatous inflammation may be present

Answer 228

Increased melanin in basal layer Normal or decreased number of more active melanocytes No elongation of rete ridges or nesting of melanocytes

Answer 229

Increased melanin in the basal layer Normal number of melanocytes (although may slight increase in NF-1 CALMs) No elongation of rete ridges or nesting of melanocytes Macromelanosomes

Answer 230

Hyperpigmented, often elongated rete ridges, usually with increased melanocyes No nests of melanocytes No solar elastosis

Answer 231

Hyperpigmented basal layer, often with elongated, clubbed rete ridges ("dirty feet"), usually with increased melanocytes No nests of melanocytes Solar elastosis

Answer 232

Epidermal changes vary greatly: atrophy, hyperplasia, papillomatosis, or horn cysts may be present Nests (theques) or cords of melanocytes (“nevus cells”) at the dermal–epidermal junction or in the dermis. Nevus cells vary greatly in size and shape, and melanin may or may not be present (melanin most likely to be present in junctional nests or upper dermal nests). Type A nevus cells are usually present in the junctional zone or superficial dermis, and appear epithelioid (more cytoplasm, larger, pale nucleus). Type B nevus cells are usually present in the mid-dermis and resemble lymphocytes (less cytoplasm, small dark nucleus). Type C nevus cells are usually present in the deeper dermis; they are more spindled and have considerable pink cytoplasm, and may form neuroid structures. A fourth type of nevus cell is the nevus multinucleated giant cell. These are usually more prevalent in the superficial dermis and have clumped nuclei, but sometime they exhibit a rosette of nuclei Usually no inflammation, unless the lesion is irritated

Answer 233

Symmetrical sharply demarcated lesion Epidermal hyperplasia with rete reidges often clutching melanocytic nests Melanocytic nests (junctional, dermal, or compound), spindle-shaped or epithelioid, or both Clefts, often around melanocytic nests, sometimes pagetoid Bizarre multinucleated or atypical melanocytes often in superficial portion of lesion, sometimes with mitoses limited to superificial portion, often with angulated or vertically orientated shape Maturation Melanin absent, sparse or prevalent Hyaline (Kamino) bodies sometimes at DEJ Vascular dilation Lymphocytic infiltrate more likely patchy than lichenoid HRAS mutations 10-30%, ALK1 10%, NTRK 16%, BRAF 5%

Answer 234

Elongated, clubbed rete ridges often similar to a lentigo Poorly circumscribed melanocytic nests at the dermal–epidermal jnction, often bridging between rete ridges. Single melanocytes predominant over nests (so-called lentiginous hyperplasia) Junctional melanocytes often extend beyond the dermal melanocytes at the periphery of the lesion (shoulder phenomenon) if it has a dermal component Cytologic atypia of melanocytes (absent in most cases per some authors, including this author, while others say it is the most important feature!). Nuclear size has been used as part of the grading: mild = melanocytic nuclear size less than 1.5 × the size of basal keratinocytes, moderate = 1.5–2 ×, and severe 2 × Maturation of melanocytes in the dermis if dermal nests are present (cells are smaller and less atypical in deepest portion) Fibroplasia in the papillary dermis around the junctional melanocytes, as if the body is walling off these melanocytes with collagen. Some think this is just compression of collagen by elongated rete ridges Mild to moderate perivascular lymphocytes in the dermis. An ordinary nevus should not have lymphocytes within it unless it is an irritated, halo, or Spitz nevus

Answer 235

Epidermis normal Spindle-shaped dendritic melanocytes in the dermis associateed withi abundant fine granules of melanin Melanophages, macrophages that have phagocytized clumps of melanin Sclerosis of collagen common GNAQ mutation in about 50-80%, GNA11 mutation in about 7%

Answer 236

Epidermis is normal Spindle-shaped dendritic melanocytes in the dermis associated with abundant fine granules of melanin Melanophages usually not present

Answer 237

Epidermis normal Spindle-shaped dendritic melanocytes in the deep dermis associated with abundant fine granules of melanin Melanophages usually not present

Answer 238

Epidermis is normal, atorphic, hyperplastic or ulcerated (worse prognosis) Asymmetrical proliferation of melanocytes, often with poorly demarcateed border (except in nodular melanoma) Atypical melanocytes, small, spindled or epithelioid, often with finely dusted with melanin, arise at the dermal-epidermal junction and invade the dermis Mitoses are often not present Poor maturation Pagetoid melanocytes often Lymphatic/vascular invasion may be present Lichenoid lymphocytes in the dermis (perivascular less often) or sparse Precursor lesion (1/3 of cases) Regression - vascular fibrous tissue in the papillary dermis, sometimes with melanophages

Answer 239

Enlarged, otherwise normal sebaceous gland, often with a large central orifice Solar elastosis frequent

Answer 240

Epidermal hyperplasia and papillomatosis Many normal or enlarged sebaceous glands, usually unassociated with mature hair shafts. Early in childhood, the entire pilosebaceous unit is poorly developed and appears as small buds Many apocrine glands Basaloid hyperplasia, true basal cell carcinoma (BCC, less than 5% incidence, some authors call them trichoblastoma instead) syringocystadenoma papilliferum, trichilemmoma, or other adnexal tumors commonly develop within a nevus sebaceus after puberty

Answer 241

Distinctly circumscribed lobular tumor of mature sebaceous cells (sebocytes, which may have a crenulated outline or surface indented by the sebaceous material) and basaloid (germinative) cells, with about 50% or more of the cells being mature sebaceous cells Minimal cytologic atypia, although mitoses may be prevalent in some lesions

Answer 242

Features of BCC (18.14) with less than 30% mature sebocytes (often only focal areas).

Answer 243

Pagetoid cells sometimes in the epidermis or conjunctiva Disordered invasion of dermis by poorly defined lobules of basaloid or squamoid cells and poorly developed sebaceous cells Moderate to severe atypia Oil-red-O or Sudan black stain for lipid: must be done with frozen section Positive staining fo EMA, is more weekly positive or negative in both BCC and SCC Androgen receptor often positive (unlike BCC/SCC) Adipophilin positive in a membranous pattern (as opposed to granular patterin in clear cell SCC or BCC)

Answer 244

Large open or closed comedo-like lesions (sometimes resembling a cyst if there is no orifice) into which numerous small hair follicles with trichohyaline granules and vellus hairs open Fibrotic stroma

Answer 245

Circumscribed basaloid tumour islands, often in a reticulated pattern or cribriform pattern, sometimes resembling poorly developed hair follicles Horn cysts common Peripheral palisading of nuclei, but no artifactual retraction between tumour and stroma Loose stroma with many fibroblasts surround basaloid islands Papillary mesenchymal bodies (clusters of fibroblasts adjacent to epithelial buds as in the germinative portion of the normal hair papilla) Brooke-Spiegler association

Answer 246

Circumscribed nodule resembling a cyst in the dermis, sometimes with a squamous epithelial lining of the periphery Basaloid cells in younger lesions, especially around periphery of nodule. Mitoses common even in benign lesions Shadow (ghost) cells, which have a pale, empty space where the nucleus used to be, with abundant pink cytoplasm. Transitional cells may be present, not to be confused with transitional epithelium, with pyknotic nuclei in the process of becoming shadow cells Shards of keratinous debris, shadow cells, calcification, or ossification may be predominant in older lesions (basaloid cells gradually decrease in number) Foreign body multinucleated giant cells and granulomatous inflammation (1.51) often present as a reaction to abundant keratin Gardner syndrome and myotonic dystrophy

Answer 247

Arises in a pilar cyst Proliferated wall with squamous eddies and paerls Abrupt trichilemmal keratinisation without a granular layer Clear cells sometimes present Can be malignant

Answer 248

Hyperkeratosis with downward lobular growth of epidermis Keratinocytes are clear cells because of glycogen within the cells (PAS positive, diastase labile) Thin rim of basal cells palisade at edge of lobule of clear cells Thickened basement membrane sometimes (PAS positive, diastase resistant) CD34 and pankeratin is positive in the epithelial cells, but not commonly done Cowden, Bannayan-Riley, Proteus (PTEN mutations)

Answer 249

Hair follicle with thin extensions of epithelium into surrounding mucinous stroma (fibrofolliculoma) Loose fibrosis with thin collagen bundles and blood vessels localised to a subepidermal area adjacent to a hair follicle without follicular extension in older lesions (trichodiscoma) Birt-Hogg-Dube

Answer 250

Circumscribed large basaloid neoplasm usually greater than 1 cm Location deep dermis or subcutaneous tissue No solar elastosis, no connection to surface epithelium No significant numbers of mitoses or cytologic atypia

Answer 251

Basaloid hyperplasia of the epidermis sometimes Increased size or number of apocrine or eccrine glands

Answer 252

Circumscribed tumor in the dermis with many maze-like glandular spaces, apocrine differentiation, and papillary folds Usually no connection of the tumor to the epidermis Usually minimal inflammation around the tumor

Answer 253

Papillomatous epidermis connecting to underlying tumor Cystic space within tumor opens to surface of skin. Tumor lined by squamous epithelium in the upper portion; lower portion lined by sweat glandular epithelium Apocrine decapitation secretion usually present (sometimes is eccrine) Papillary projections into cystic space Plasma cell infiltrate around tumor Nevus sebaceus is often present as a precursor lesion

Answer 254

Tumour of basaloid cells in the dermis arranged in islands that often fit together like a jigsaw puzzle. One type is larger and has paler nucleus than the other Hyalinised cylinders (thickened basement membrane) around each tumour island Hyalinised droplets often within tumour Sweat duct lumina often present within tumour islands Brooke–Spiegler syndrome

Answer 255

Circumscribed tumor, many glandular spaces with apocrine decapitation secretion and papillary projections into the lumina, sometimes filling the lumina Tumor often connects to surface of epidermis Infiltrate of lymphocytes or plasma cells around the tumor sometimes

Answer 256

Epidermis sometimes hyperplastic Circumscribed tumor in dermis or subcutaneous tissue consisting of many glandular spaces Apocrine decapitation secretion usually present Papillary projections without stroma extend into the lumina of the tubules No connection to the surface epithelium

Answer 257

Proliferation of eccrine ducted structures in the dermis. When sectioned at an angle, they appear to resemble tadpoles or paisleys No aggressive infiltration of the deeper dermis Horn cysts may be present, and milia may coexist Stroma is often fibrotic or sclerotic

Answer 258

Circumscribed dermal tumor consisting of many glandular spaces with eccrine (sometimes apocrine) differentiation Papillary projections into the lumina only in some portions of the neoplasm Focal or no connection to the surface epithelium Fibrous stroma Positive staining for CEA and S-100

Answer 259

Nodular tumor in the dermis or subcutaneous tissue made up of mainly one cell type of basaloid cells, sometimes with focal connection to epidermis Sweat duct lumina usually present within the tumor, varying from small ducts to large cystic spaces Usually eccrine differentiation, rarely apocrine decapitation secretion is present Hyalinized collagen in the stroma sometimes Keratinous cysts sometimes

Answer 260

Tumour of cuboidal or basaloid "poroid" cells within the lower portion of an acanthotic epidermis extending into the dermis Often sharp demarcation or moat between normal epidermis and tumour Tumour cells may be clear due to glycogen accumulation Small sweat ducts usually present within tumour

Answer 261

Sharply demarcated nodules of basaloid cells in dermis or subcutaneous tissue (“blue balls”) Almost never any connection to the epidermis Basaloid cells are often said to be of two types, which might not be so apparent: one is more pale with more cytoplasm than the darker cells Basaloid cells tend to be arranged in rosettes, sometimes called trabeculae Sparse small sweat ductal lumina usually present Lymphocytes with Langerhans cells usually scattered in the stroma and in the epithelial aggregates Stroma often vascular

Answer 262

Epithelial islands small to medium sweat ductal structures, eccrine or apocrine Prominent mucinous stroma (positive with acid mucopolysaccharide stains) eventually becoming chondroid Hyalinised areas in the stroma (sometimes)

Answer 263

Tumor infiltrating the dermis and consisting of ductal or glandular structures Atypia (hyperchromatism, pleomorphism, increased numbers of mitoses) or necrosis often present

Answer 264

Epidermis may be atrophic, hyperplastic or ulcerated Lichenoid or diffuse, less commonly just perivascular: atypical lymphocytes, sometimes with cerebriform nuclei, with eosinophils and plasma cells Epidermotropism of the atypical lymphocytes: patrier microabscesses (less prominent in older nodules), bare underbelly sign (lymphocytes preferentially on the epidermal side of blood vessels, heading towards the epidermis) Spongiosis usually not seen in most cases, unlike eczema. MF has too much epidermotropism for too little spongiosis (“too much for too little”) Follicular mucinosis sometimes present Most lymphocytes exhibit positive staining with T-cell markers (CD2, CD3, CD5), most often with increased T-helper cells (CD4) and fewer suppressor-cytotoxic T cells (CD8), the normal 2:1 ratio of CD4:CD8 is usually more than 3 : 1. Loss of pan-T-cell markers such as CD7, and less commonly CD43 or CD5, has been stressed as helpful, but this may not be as specific as advertised Identification of CD25 (IL-2 receptor) positive cells is useful prior to therapy with denileukin diftitox (Ontak). Positive staining for CD52 is useful for possible alemtuzumab (anti-CD52, Campath) treatment. Positive staining for cytotoxic proteins (granzyme, perforin, TIA-1) indicates more aggressive subtype (some would not classify this as true mycosis fungoides) Clonal T-cell receptor (TCR) gene rearrangements may be present in 60% of patients with patch stage MF, 65% of more advanced MF, and 20% of benign inflammatory conditions. The gene rearrangement is usually alpha–beta, but sometimes gamma–delta Papillary dermal collagen often said to be wiry, resembling fettuccine, but this is overrated as a diagnostic help

Answer 265

By definition, more than 1000 Sezary cells per cubic millimeter in the peripheral blood (large cerebriform atypical CD4 + lymphocytes greater than 14 microns). The CD4 +:CD8 + ratio is often more than 10 : 1 with flow cytometry with most cells are CD7 −. The Sezary cells are negative for CD4. CD26 loss with flow cytometry has been found in 50% of cases, but this is less important than loss of T-cell markers CD2 and CD3, since loss of CD26 is found in 33% of cases of MF, and 15% of cases of benign dermatitis. Otherwise routine histology and immunopathology similar to MF (24.1). In some cases the skin biopsy is non-specific and the diagnosis is made from the blood. Clonal T-cell gene rearrangments in skin or blood as in MF.

Answer 266

Histology and TCR often similar to MF ``` CD3+, CD4+ CD25 positive (unlike MF) ``` Gene rearrangements often present

Answer 267

``` Lobular panniculitis (often lace-like pattern of lymphocytes rimming adipocytes), without significant dermal or epidermal involvement The malignant small lymphocytes are usually CD3 +, CD8 +, granzyme +, TIA-1 +, perforin + (cytotoxic phenotype). Sometimes the lymphocytes may be larger with more cytologic atypia CD68 + macrophages often exhibit cytophagocytosis of erythrocytes or nuclear debris (“bean bag cells”) Sometimes an alpha–beta (α–β) T-cell receptor gene rearrangement is present (BF-1 positive) ```

Answer 268

Epidermal necrosis often, or ulceration Nodular infiltrate of ordinary lymphocytes, very atypical CD-30 positive activated T lymphocytes iwth epidermotropism into the epidermis Neutrophils and eosinophils sometimes present Extravasated erythrocytes, often with red blood cells in the epidermis Multiple subtypes 10% risk of progression to NHL/MF

Answer 269

Epidermis often ulcerated, sometimes pseudocarcinomatous hyperplasia Diffuse or perivascular polymorphous infiltrate of atypical lymphocytes, histiocytes, plasma cells, and eosinophils Epidermotropism sometimes, invasion of adnexa and nerves common Infiltration of blood vessel walls by lymphocytes, sometimes with changes suggesting vasculitis (necrosis of vessel walls, with thrombi, 1.145) CD2 +, CD56 +, TIA-1 +, but with frequent loss of T-cell markers CD3, CD4, CD5, or CD7 (therefore formerly called null cells). Epstein–Barr positive (by in situ hybridization, for example) Usually negative for gene rearrangements

Answer 270

Nodular or diffuse atypical lymphocytes with prominent epidermotropism Less involvement of the fat than the other two conditions in this section CD3 +, CD7 +, CD8 +, CD45RA +, TIA-1 +, granzyme +, perforin +. CD4neg, CD30neg, CD56neg Clonal T-cell receptor (TCR) gene rearrangement often present (usually BF-1 +)

Answer 271

Erosion, necrosis, or ulceration common Lichenoid or nodular pattern of atypical lymphocytes with prominent epidermotropism and frequent extension into the fat Papillary dermal edema, and lymphocytic angiotropism and vascular destruction are common Macrophages with phagocytosis of lymphocytes or erythrocytes (hemophagocytic syndrome) common Lymphocytes are CD3 +, CD5 +, CD56 +, CD57neg, CD30neg, CD4neg. CD8 variable. Cytotoxic phenotype: TIA-1, granzyme, perforin positive. Epstein–Barr negative γ–δ T-cell gene rearrangement present by definition (not α–β)

Answer 272

Diffuse small to medium-sized lymphocytes in dermis or subcutaneous fat, sometimes epidermis CD3 +, CD4 +, CD8neg, CD30neg, sometimes CD7 depleted. Clonal T-cell receptor gene rearrangements may be present

Answer 273

Usually diagnosed from lymph node rather than skin Diffuse lymphocytes, macrophages, eosinophils, plasma cells, and immunoblasts in the dermis Superficial venules have prominent endothelial cells (“high endothelial venules”) CD3 +, CD4 +, CD5 +, CXCL13 +, CD21 + (non-malignant follicular dendritic cells around vessels), CD8neg. CD10 may be positive T-cell receptor gene rearrangements often present

Answer 274

``` Diffuse lymphoid infiltrate in dermis and fat, sparing epidermis Not angiocentric (no vascular destruction), unlike other CD56 + lymphomas in 24.6 CD4 +, CD56 +, CD123 + (plasmacytoid dendritic cells), CD303 + (BDCA-2), TCL-1 +, CD3neg, CD20neg, myeloperoxidase negative (unlike myeloid leukemia). The mnemonic “123-4-56” has been used to remember the first three important staining features No clonal T-cell receptor gene rearrangement; Epstein–Barr virus negative ```

Answer 275

Diffuse or nodulra lymphoid infiltrate in dermis and fat, sparing epidermis Germinal centers with reduced mantle zones and reduced tingible body macrophages are present except in the “diffuse type”, and Ki-67 proliferation is decreased compared to normal germinal centers (see below) CD20 +, CD79a +, Bcl-6 +. CD10 + in the follicular type (all four of these are positive outside germinal centers, with loss inside germinal centers, but not in the diffuse type). Bcl-2neg, CD5neg, CD43neg, MUM-1neg, FOX-P1neg (worse prognosis if positive). CD21 + follicular dendritic cells show an irregular network Usually no t(14;18) translocation

Answer 276

Nodular or diffuse small lymphocytes with eosinophils and plasma cells in dermis and superficial fat, sparing epidermis Inverse pattern of small dark reactive lymphocytes, surrounding malignant clone with increased pale cytoplasm (compared to LN) Folliculocentric/syringotropic orientation Reactive germinal centers present in 30% Malignant clone positive for CD20, CD79a, bcl-2. Sometimes positive for CD23. Negative for CD43, CD5, CD10, bcl-6. Often monoclonal kappa or lambda restriction. Reactive CD3 + T cells may equal the numbers of CD20 + B cells in many cases, with only 15% of cases really having a predominance of CD20 + cells even though this is a B-cell lymphoma Often heavy chain gene rearrangement Translocation t(14;18) in small number of cases

Answer 277

Dense infiltrate of large atypical lymphocytes with prominent nucleoli in the dermis Grenz zone common but epidermotropism may be present Adnexa often destroyed B cells positive for CD20, CD79, MUM-1, FOX-P1, BCL-2/BCL6, sometimes CD10+ Negative for CD30 despite larger cells J heavy chain rearrangements can be found

Answer 278

Epidermis usually normal without epidermotropism Nodular or diffuse infiltrate of lymphoid cells in the dermis Grenz zone common Single filing of cells between collagen bundles often Cytologic atypia and mitoses often Cells often fragile, may show crush artifacts Monoclonal staining common Positive staining for B cell markers such as CD20, CD79a, PAX-5 Reactive T cells are often present TIA-1 negative

Answer 279

Diffuse plasma cells in the dermis, often atypical: multinucleated, Russell bodies, Dutcher bodies sometimes present. Mitoses prevalent Plasma cells are CD38+, CD138+, CD56+, CD79a often positive CD20, CD45 usually negative Methyl green pyronin stains the cytoplasm of plasma cells red, but not commonly done Immunostaining for kappa or lambda light chains, IgG, IgA, or IgD often reveals monoclonality

Answer 280

Intravascular large atypical lymphocytes, often with occlusion or thrombi Angiotropic lymphoma Most cases are CD20+, CD79+, sometimes CD5,10,11a,bcl-2,MUM-1 CD10, EBER and bcl-6 in minority of cases Bcl-1 negative

Answer 281

Epidermis unremarkable or often hyperplastic Nodular or diffuse dermal infiltrate of mostly lymphocytes, also with mixed sparse or many eosinophils, macrophages, multinucleated giant cells, or plasma cells Grenz zone, with no lymphocytes in the epidermis Germinal centres with tingible body macrophages sometimes present Normal germinal centres are bcl-6+ and CD1-+ with CD21+ and/or CD23+ follicular dendritic cell network bcl-2 is negative Endothelial hyperplasia common

Answer 282

Epidermis usually normal, often with a Grenz zone Polymorphous nodular or diffuse lymphocytes in the dermis of atypical Hodgkin's cells (CD15/30+, CD45R- TIA-1-) eosinophils, plasma cells, neutrophils, multinucleated giant cells CD45, CD20, CD79a, PAX5, bcl-6 are variable depending on the subtype Reed-sternberg cells are difficult to find in the rare skin lesions of Hodgkins

Answer 283

Epidermis usually normal, without epidermotropism Nodular or diffuse cells in the dermis, often with a Grenz zone Infiltrating cells may appear monomorphic, atypical, or immature, and often are fragile, showing crush artifacts Single filing of cells between collagen bundles sometimes Most leukemias will stain in the skin with the less specific stains, CD43 and CD45 (leukocyte common antigen), and are negative with most T-cell stains such as CD3 and CD45RO. Mature B-cell stains such as CD20 are negative, except sometimes it is weakly positive in CLL Gene translocations can be identified in some leukemias, a rapidly changing area beyond the scope of this book

Answer 284

Perivascular or diffuse dermal mast cells, often with a few eosinophils Dermal edema or subepidermal blister formation sometimes Mast cells usually can be recognized with H&E stain, but are better demonstrated with Giemsa, Leder, toluidine blue, tryptase, or CD117 (c-kit). CD2 and CD25 more often positive in systemic mastocytosis with bone marrow involvement

Answer 285

Epidermis may be ulcerated Epidermotropism of Langerhans cells into the epidermis is common Lichenoid or diffuse dermal infiltrate of Langerhans cells (often have atypical kidney-shaped reniform nucleus), may be foamy or resemble Touton histiocytes Polymorphous infiltrate of accompanying lymphocytes, eosinophils, neutrophils, or plasma cells often present Positive staining of Langerhans cells for CD68, S100, CD1a, CD207 (Langerin) Birbeck granules on EM BRAF V600E mutations in half of all cases

Answer 286

Bone marrow precursors of one or all three lineages may present (myeloid, erythroid, megakaryocytes), usually sparse in dermis or subcutaneous tissue (not nodular or densely diffuse) Immature myeloid cells are CD14 +, CD34 +, CD68 +, CD117 +, and CD163 +. They also stain with Leder, lysozyme, and myeloperoxidase stains Nucleated red blood cells (nucleated erythrocytes, normoblasts, erythroblasts) are positive for hemoglobin or glycophorin stains Megakaryocytes are CD41 +, CD42b +, and CD61 + Vascular or myxoid stroma

Answer 287

Epidermis normal or atrophic Proliferation of blood vessels and endothelial cells GLUT-1 positive in porliferating and involuting infantial haemangiomas (and placentas), negative in other vascular neoplasms, vascular malformations, non-involuting congenital haemangioma and rapidly involuting congenital haemangioma Claudin-1 and Wilms tumour-1 (more likely to be positive in infantile haemangioma)

Answer 288

Hyperkeratosis, epidermal rete ridges often encircle dilated vessels Dilated vessels in superficial dermis, without much endothelial proliferation Thrombi common

Answer 289

Epidermis atrophic or ulcerated, often with crust with neutrophils (pyo-) on surface Collarette of epidermis often demarcates the lesion Pyogenic granuloma is a misnomer, as it is characterized by excessive granulation tissue (“proud flesh”), often arranged in vascular lobules, rather than a granuloma. Granulation tissue is vascular proliferation in a pale stroma with an inflammatory sparse or prominent infiltrate of neutrophils or lymphocytes

Answer 290

Epidermis normal Vascular proliferation with prominent “hobnail“ endothelial cells protruding into the lumina, often associated with vacuoles Nodular or diffuse infiltrate of lymphocytes and eosinophils

Answer 291

Proliferation of blood vessels surrounded by glomus cells (monotonous cells with a dense, round nucleus and abundant pink cytoplasm), often single-filing through the stroma Stroma often pale Positive staining for smooth muscle actin in glomus cells. Desmin is positive in a minority of cases

Answer 292

Epidermis normal Cicumscribed nodule of spindle-shaped or polygonal-shaped pericytes with variable atypia Increasing number of blood vessels, sometimes with antler-like branching (stag horn) Reticulum stain shows that the pericytes are outside the reticulum fibres that surround the endothelium Malignant lesions more likely to show more extravasated erythrocytes, necrosis, more cellularity, \>4 mitoses per ten high-power fieldsd Positive staining for vimentin, CD34, p75 Negative for keratin, S-100, CD31, factor VIII-related antigen, Ulex europaeus, smooth muscle actin, desmin

Answer 293

Poorly demarcated dissecting blood vessels with irregular branching, papillary projections into the lumina, and sometimes slit-like spaces Proliferating infiltrating spindled or epithelioid atypical endothelial cells. If well-differentiated, proliferating vessels may be readily identified and atypia is mild to moderate, but poorly differentiated angiosarcomas have very pleomorphic, atypical hyperchromatic endothelial cells with many mitoses, and poorly recognizable vessels Prominent extravasated erythrocytes, sometimes hemosiderin Reticulum stain shows endothelial cells to be surrounded by reticulum fibers Positive staining with endothelial cell markers such as CD31, CD34, factor VIII-related antigen, ERG and FLI-1 (both newer nuclear stains), claudin-5 (newer membranous stain), and Ulex europaeus (an older stain). Ki-67 shows more positivity than benign vascular lesions. Myc nuclear staining or gene amplification is found in the majority of secondary radiation or lymphedema-associated angiosarcomas, but not in “atypical vascular proliferations” and the other primary types of angiosarcoma

Answer 294

Within a vein or other vascular structure, numerous papillary projections of loose connective tissue proliferate, lined by many endothelial cells without atypia or mitoses

Answer 295

Early patch-stage lesions have a subtle infiltration of the dermis by slit-like vascular spaces lined by spindled endothelial cells In the lymphangioma-like variant, vascular spaces lack erythrocytes In the angiomatous variant, mature, dilated, larger blood vessels may be dominant over the slit-like ones Older lesions may have solid areas of spindle cells (mostly endothelial cells) with slit-like vascular spaces Promontory sign sometimes present (small blood vessel and its stroma project like a promontory into a vascular space) Cytologic atypia is usually mild, and mitoses usually sparse Extravasated erythrocytes, occasional plasma cells, hemosiderin common PAS positive, Mallory trichrome positive, eosinophilic hyaline globules sometimes present, which appear to represent phagocytosed erythrocyte fragments (overrated as useful) Variable staining for vascular markers. such as CD34, which seems to work better than CD31. ERG is a new nuclear stain that works well. Ulex europaeus and factor VIII-related antigen are also positive, but utilized less commonly. Immunostaining for HHV8 is usually positive, stronger in nodules than in macules or patches, negative in other vascular proliferations

Answer 296

Epidermal hyperplasia sometimes Proliferation and dilation of lymph vessels in dermis (especially papillary dermis) or deep soft tissue, lined by endothelial cells D2-40 and Prox1 are more likely to be positive in lymphatics than in blood vessels, though they are not competely specific for this

Answer 297

Somewhat demarcated nodule in the dermis or subcutaneous tissue of spindle cells with wavy nuclei (diving dolphins), sometimes in strands said to resemble shredded carrots Pale “bubblegum” pink stroma, mucinous or myxoid Mucinous stroma stains positive for acid mucopolysaccharides Mast cells common Positive staining for S-100, CD34, PGP9.5, factor XIIIa, myelin basic protein, and neurofilaments. Bodian stain rarely performed, but should reveal axons (a type of neurite) since the neurofibroma is a neoplasm of the entire peripheral nerve, also including Schwann cells, endoneurial fibroblasts, and perineurial cells.

Answer 298

Encapsulated subcutaneous tumour with cellular areas (Antoni A) and/or oedematous myxoid areas (Antoni B) Spindle cells in Antoni A tissue line up in two parallel rows separated by an area without nuclei (Verocay bodies) Mucinous stroma stains positive for acid mucopolysaccharides Mast cells common Positive staining for S-100, CD56, Calretin, myelin basic protein (Antoni A areas) Tumour may be attached to large nerve

Answer 299

Bundles of somewhat well-delineated faciscles of peripheral nerves Stroma often fibrotic Positive staining for S-100, myelin basic protein, and neurofilaments

Answer 300

Epidermal hyperplasia, sometimes pseudoepitheliomatous hyperplasia Infiltration of the dermis or subcutaneous tissue by large cells with a granular cytoplasm and small centrally located nuclei Larger eosinophilic intracytoplasmic granules are called pustulo-ovoid bodies of Milian Granules are positive with PAS stain or PTAH but usually negative with lipid stains Tumour stains positive for myelin basic protein, NSE, calretin, S-100, NKI-C3, CD68

Answer 301

Epidermis atrophic Atrocytes and neurons in a pale neurofibrillary stroma Multinucleated giant cells common Calcification sometimes Fibrotic stroma, vascular ectasia common Glial fibrillary acid protein stains glial cells, neuron-specific enolase stains the neurons Bodian silver stain or neurofilament stain demonstrates neurites (axons) extending from neurons

Answer 302

Sharply demarcated connection throguh skull to central nervous system Meningothelial cells are epithelioid or spindled, with vesicular nuclei abundant pink cytoplasm with indistinct borders, often in a hyalinised stroma. Wide variation in patterns. Usually no cytologic atypia and no mitoses unless anaplastic Pseudovascular spaces sometimes, dense fibrous stroma often Minengothelial whorls and psammoma bodies sometimes present Positive staining for vimentin and epithelial membrane antigen and claudin-1 in meningothelial cells with variable staining for S-100, neuron-specific enolase and cytokeratin

Answer 303

Pale myxoid sharply demarcated or encapsulated dermal or subcutaneous nodule divided into lobules or fascicles by fibrous septa Spindle cell nuclei may be pleomorphic, sometimes epithelioid Mucinous stroma stains positive for acid mucopolysaccharides Positive staining for S-100, GFAP, type IV collagen, weak for NSE; negative for axons (neurofilament immunostain or Bodian stain), EMA, keratin

Answer 304

Diffuse dermal atypical small blue cells with minimal cytoplasm, in clusters, rosettes, and cords (trabeculae) in the dermis, usually with many mitoses Epidermotropism of the small cells, or coexisting bowenoid change may be present Positive staining often with neuron-specific enolase (NSE), epithelial membrane antigen (EMA), CD56, neurofilament, synaptophysin, chromogranin, or argyrophil stains. There is often a classic paranuclear dot staining patternwith low molecular weight keratin, such as CK20, cam 5.2, AE-1. Negative staining for S-100, TTF-1, CK5/6, CEA, and LCA. Some rare CK20neg cases will stain with CK7, but CK7 is usually negative. Bombesin may be positive in Merkel cell carcinoma, but some studies found it to be negative and more likely positive in metastatic neuroendocrine carcinoma in the skin, so it is mainly used as an old exam question and not in clinical use. CM2B4 stains the large T-antigen of the polyoma virus, and is highly specific for MCC but not sensitive (only 60% of MCCs are positive). P63 positivity is said to indicate poor prognosis and bcl-2 a favorable prognosis

Answer 305

Poor circumscription of mass Proliferation of spindle cells with wavy nuclei in a pale mucinous stroma Often p75 +, CD56 +, PGP9.5 +, and nestin +. Sometimes weakly S-100 +. Ki-67 often positive in ≥ 20% of cells, Sox10131 may be positive, but some authorities say this is more common in benign cellular schwannomas. Loss of INI-1 (SMARCB1) in 50% of cases (more commonly lost in epithelioid sarcoma, 27.14). H3K27me3 staining is lost in 70% of cases, but not in melanomas, synovial sarcomas, and myoepithelial tumors. Cytologic atypia (pleomorphism, hyperchromatism, increased numbers of mitoses) often present, but not always prominent Necrosis sometimes present Malignant transformation of neurofibroma in NF1

Answer 306

Epidermal hyperplasia often, sometimes with flattenede 'tabled' rete ridges or basaloid proliferatoin simulating a basal cell carcinoma Hyperpigmented basal layer often Poorly circumscribed proliferation of boomerang-shaped spindled fibroblasts or histiocytes in the dermis, often whorling about, blending into the surrounding dermis like a bomb that was dropped in the dermis, sometimes extending into the subcutaneous fat Multinucleated giant cells, Touton giant cells, foamy histiocytes sometimes Haemosiderin often Large bundles of collagen (keloidal collagen) often at the periphery Positive for CD68, CD163, Factor XIIIa Negative for CD34

Answer 307

Epidermis atrophic or normal, often with loss of rete ridges Subepidermal blister artifact is common Bands of fibroblasts and dense collagen, often oriented parallel to the epidermis Young scars may have a pale or mucinous stroma and more fibroblasts, sometimes extravasated erythrocytes, while older ones have more collagen, less paleness, and fewer fibroblasts (more sclerotic) Blood vessels tend to be more perpendicularly oriented with respect to the epidermis

Answer 308

Collagen oriented concentrically around follicles or oriented more perpendicular to the epidermis Sometimes increased numbers of stellate, plump fibroblasts Few dilated blood vessels TSC Familial myxovascular fibromas Multiple endocrine neoplasia type 1

Answer 309

Pedunculated papule, epidermis often extends almost completely around the specimen when it is sectioned Papillomatosis and acanthosis common, sometimes epidermal atrophy Dermis consists of loose connective tissue that is often pale Dilated blood vessels often

Answer 310

Massive orthokeratosis, usually no parakeratosis, with acanthosis Thickened collagen in the dermis, often oriented parallel to the long axis of the lesion

Answer 311

Poorly demarcated nodule with increased collagen and normal, decreased or increased elastic fibres Sometimes easily missed ``` Shagreen patch of TSC (no increase in elastic tissue) Naevus elasticus (increased elastic tissue) Buschke-ollendorff syndrome ```

Answer 312

Dense band of collagen and many plump myofibroblasts Eosinophilic cytoplasmic inclusion bodies (3-10 microns) in the myofibroblasts, often adjacent to the nuclei Easier seen with PTAH, actin or trichrome stains, negative with PAS

Answer 313

Subcutaneous somewhat circumscribed nodular proliferation of myofibroblasts in a loose, mucinous stroma, resembling “tissue-culture fibroblasts” Muscle-specific actin or smooth muscle actin often positive, but desmin is usually negative. Vimentin and CD68 positive. S100, caldesmon, and CD34 are negative Sometimes infiltration through muscle or along fibrous septa of fat Fibroblasts may be moderately pleomorphic, hyperchromatic, or may show increased mitoses that are not atypical Multinucleated osteoclast-like giant cells may be present Often prominent vascularity, sometimes slit-like spaces, extravasated erythrocytes Lymphocytes often present within the nodule to a greater extent than usual in a sarcoma, especially at the margin

Answer 314

Sharply demarcated localized lobule Proliferation of fibroblasts and histiocytes, sometimes foamy Large osteoclast-like giant cells with many haphazard nuclei usually present Hemosiderin often present

Answer 315

Epidermis normal, atrophic, or ulcerated (rarely hyperplastic) Very cellullar proliferation of thin spindled fibroblasts and collagen in the dermis, extending into the subcutaneous fat Cartwheel pattern (fibroblasts whorl around like spokes of a wheel) or storiform (whirligig or mat-like) pattern Usually no foamy cells or multinucleated giant cells, unlike dermatofibroma Infiltration of fat in a fascicular or honeycomb pattern Mast cell counts are less frequent in tumours that have more mitoses or larger size Cytologic atypia mild to moderate, very few mitoses CD34 +, nestin +, stromelysin-3-neg, factor XIIIa-neg, D2-40-neg (all five opposite of dermatofibroma) S-100 and SOX10 are negative

Answer 316

Subcutaneous cellular proliferation of fibroblasts, histiocyte-like cells, and bizarre giant cells Severe pleomorphism, hyperchromatism, many bizarre cells or highly atypical mitoses often Vimentin +: variable positivity with fibrohistiocytic markers CD68, alpha-1 antitrypsin, and alpha-1-antichymotrypsin. Variable positivity with muscle markers desmin and actin. CD34 is negative.

Answer 317

Dermal cellular proliferation of bizarre spindle cells, epithelioid cells, or multinucleated giant cells, and sometimes foamy cells (hence the name xanthomatous, but it frequently does not have this feature), often extending up against the epidermis Severe pleomorphism, hyperchromatism, many very atypical mitoses Solar elastosis Positive staining for vimentin, CD68, S100A6, antichymotrypsin, antitrypsin, procollagen-1, and strongly positive for CD10. CD99 positive in 70%. Sometimes calponin, SMA or desmin positive in minority of cases. EMA may be focally positive. CD163 is more specific for histiocytes than CD68, but positivity for CD163 varies in studies of AFX. Negative for CD31, CD34, S-100 (except few dermal dendrocytes), pankeratin, SOX10, p40, and p63, with few exceptions. Variants with granular cells, osteoclastic giant cells, myofibroblastic cells, CD30 + lymphomatoid cells, or with keloidal, chondroid or bony areas have been described

Answer 318

Subcutaneous densely cellular proliferation of uniform spindle cells, sometimes with a herringbone pattern (nuclei radiate off on either side of a central “vertebral” column) Cytologic atypia mild to moderate, depending upon how well differentiated it is. Necrosis and mitoses common Vimentin +. Negative staining for pankeratin, S100, CD34, desmin, SMA

Answer 319

Poorly circumscribed often ulcerated proliferation of polygonal atypical epithelioid cells and spindled cells, often palisade around central necrosis, resembling a palisading granuloma Pleomorphism, hyperchromatism, numerous mitoses Lymphocytes common, especially at tumor periphery Positive staining with both pankeratin and vimentin (hence the tumor’s name, which refers to epithelial-like staining with keratin, as well as sarcomatous staining with vimentin). EMA is also positive. ERG and FLI-1 positive in 60–70%. D2-40 + in 60% and CD34 + in 50% of cases. Loss of INI-1 (SMARCB1) expression in 90%; this loss also found in half of cases of malignant peripheral nerve sheath tumor (26.9).

Answer 320

Dense hyalinized collagenous neoplasm with poorly defined borders Scattered fibroblasts, sometimes with corkscrew nuclei (may be more cellular in early lesions) without atypia or mitoses Nuclear staining for beta-catenin is usually found in fibromatosis, but negative in fibrohistiocytic tumors or sarcomas

Answer 321

Spindle or epithelioid fibroblasts tend to palisade around areas of dense collagen and calcification Cartilage may form in the calcified areas in older lesions

Answer 322

Poorly demarcated, paucicellular nodule of vimentin + stellate spindle cells in vascular myxoid stroma. Occasionally multinucleated cells may be present Variable staining for S100, CD34, factor XIIIa, SMA, MSA. Desmin is negative Often contains epithelial strands, cysts, or trichoblastic changes Minimal cytologic atypia, but mitoses may be present

Answer 323

Fascicles of spindle or epithelioid cells in complex plexiform pattern Nodular aggregates of CD68 +, SMA + histiocytes, multinucleated giant cells , and lymphocytes, suggesting granulomas seen in an infectious process Mild to absent pleomorphism, mitoses rare Extravasated erythrocytes and hemosiderin often May contain myofibroblasts positive for actin

Answer 324

Ill-defined subcutaneous nodule with three components: whorled cellular islands of round or spindle cells in a myxoid stroma, hypocellular fibrous fascicles, and islands of adipose tissue

Answer 325

Spindle cell nodule said to have a “patternless pattern.” Slit-like staghorn vascular channels Immunoprofile is vimentin +. CD34 + in 90% and CD99 + in 70% of cases. S100, EMA, and actin sometimes positive. Staining is negative for factor XIIIa. Characteristically positive nuclear staining for STAT-6 (a surrogate stain for the NAB2-STAT6 fusion gene that is relatively specific for this tumor), and has a more benign course than DFSP despite being CD34 +

Answer 326

Clear cells within a dermal nodule, accentuated in perivascular distribution Immunoprofile may suggest a melanocytic tumour, except that S100 is negative HMB-45, MiTF, NKI-C3, PAS (glycogen) are positiev. MART-1, desmin and CD68 are variable. SMA, pankeratin, and EMA are negative TSC1/TSC2 mutatinos are common, less common is TFE3 gene rearrangements

Answer 327

Dermal tumour with features of SCC, keratin pearls/squamous eddies if well differentiated with no connection to the epidermis Pleomorphism and hyperchromatic nuclei, increased numbers of mitoses, more prominent if poorly differentiated Usually not possible to determine the site of origin of the tumour based upon histologic features Pseudoglandular spaces without mucin may be due to acantholysis Positive staining for pankeratin, CK5/6, other keratins p40 and p63 usually positive

Answer 328

Tumour in the dermis with variable small glandular formations or signet-ring cells Pleomorphism, hyperchromatism, increased number of mitoses Mucin stains stains mucin Site usually not possible to determine but sometimes staining can be helpful CK7, CK20 (colon CK20+, CK7-; lung usually CK7+, CK20-; breast/ovarian CK7+m prostate CK7-)

Answer 329

Tumour nodules or single-filing strands with pleomorphic, hyperchromatic nuclei, increased numbers of mitoses in the dermis or in the lymphatics or blood vessels. Nuclei sometimes appear somewhat square or rectangular, lined up like vertebral body-like structures Epidermotropism may occur as in Paget's disease Glandular formation or "signet" rings sometimes present, may contain mucin + pankeratin, CK7, GCDFP, mammaglobin, androgen receptor, Sox10/S100 - CK20 usually Her-2 staining poor prognosis GATA3, low expression poor prognosis

Answer 330

Tumour lobules in the dermis, often surrounded by epidermal collarette Large clear cells (containing glycogen and lipid) with central nuclei that usually are only mildly atypical Vascular stroma, often with extravasation of erythrocytes and haemosiderin Positive staining for both

Answer 331

Diffuse infiltration of the dermis by nodules or cords of cells with atypical small round nuclei and little cytoplasm, often increased number of mitoses

Answer 332

Spindle cell infiltration of the dermis in most cases, although sometimes can be epithelioid Positive staining for vimentin, with negative staining for pankeratin in most cases

Answer 333

Adipose present in superficial dermis Increased dermal blood vessels often

Answer 334

Proliferation of normal-appearing adipose in the subcutaneous fat Sometimes sharp demarcation (rarely a capsule) from normal adipose

Answer 335

Subcutaneous tumour (poorly circumscribed or encapsulated) of immature fat cells with lipoblasts (lipid vacuoles displace the nuclei) Mucinous stroma

Answer 336

Subcutaneous encapsulated tumour of mulberry cells (large cells with a central nucleus and multivacuolated granular cytoplasm), sometimes mixed with mature adipocytes

Answer 337

Tumour in subcutaneous fat or soft tissue consisting of cells containing lipid with variable differentation toward adipose tissue Lipoblasts (cells with several lipid vacuoles displacing the nuclei) or signet-ring cells (single lipid vacuole displacing the nucleus)] S-100 protein, calretin sometimes positive Molecular studies can be performed such as FISH, CGH, qPCR

Answer 338

Proliferation of benign smooth muscle bundles, with blunt ended cigar-shaped spindle cell nuclei and abundant pink cytoplasm on longitudinal section and round nuclei with vacuoles around them on cross-section Positive red staining with trichrome and immunostaining with desmin, muscle-specific actin, or smooth muscle actin Reed syndrome

Answer 339

Smooth muscle proliferation Atypical pleomorphic nuclei with hyperchromatism, increased numbers of mitoses, necrosis Desmin, muscle specific actin, calponin, caldesmon, HHF35, S100/CK uncommonly positive Myofibrils can be identified with PTAH stain

Answer 340

Eosinophilic bony tissue in the dermis or subcutaneous fat, osteocytes (within lacunae) usually present, osteoclasts (multinucleated cells) sometimes present, osteoblasts sometimes present, distinct trabeculae sometimes present Calcification may be present Haemopoiesis is rarely present within the bone Albright's hereditary osteodystrophy Gardners syndrome Naevus of Nanta

Answer 341

Endometrial glands, straight or tortuous, lined by a pseudostratified columnar epithelium with active secretion resembling apocrine glands CD10+, atypical fibrovascular myxoid stroma Extravasated erthrocytes and haemosiderin common

Answer 342

Pedunculated papule or nodule containing numerous vellus hair follicles and often cartilage

Answer 343

Ectopic gastric, small intestinal or colonic intestinal epithelium with goblet cells present within eroded periumbilical skin Diffuse lymphocytes common in the stroma

Answer 344

Epidermis with mild papillomatosis and hyperpigmentation Increased smooth muscle bundles Mammary glands and ducts present in dermis and subcutaneous fat

Answer 345

Focal parakeratosis Focal spongiosis Perivascular lymphocytes