Dermatopathology - Entities & Features Flashcards
Clear cell acanthoma
Clear demarcation from epidermis
Often neutrophils present
PAS + showing abundant glycogen
Poroma
Small monomorphic cells Epidermis ‘raining down’ Sharp demarcation of epidermis to dermis Glandular structures in dermis Connected to basal layer of epidermis Forms vertically oriented columns Ductal spaces
Trichilemmoma
Acanthosis in epidermis
Eyeliner sign / peripheral palisade
Some koilocytic like changes at edges of lesion
Clear cell change due to glycosylation of cytoplasm
Overlying hypergranulosis and hyperkeratosis
Fibroepithelioma of pinkus
Fenestrated strands off epidermis
BCC like areas in scaffold
PHLDA1 marker - less staining in basaloid areas , more staining in pink areas
Tumour of follicular infundibulum
Epidermal epithelial growth with a plate like configuration and multiple connections to the epidermis
- keratinocytes have glycogenated appearance resembling those of outer root sheath
Prominent surrounding basement membrane
Elastosis perforans serpinosa
- extrusion of elastin fibres / transepidermal elimination
- associated folliculitis
- can have overlying parakeratosis with neuts
Folliculitis de calvans
Plasma cells Polytrichia Scarring fibrosis Neutrophilic abscesses Hair shaft granulomas Lymphocytes
Granular cell tumour
Overlying epidermis may show pseudoepitheliomatous hyperplasia
Proliferation of large to polygonal cells with granular eosinphilic cytoplasm in sheets
Individual cells with indistinct borders, small round centrally located nuclei
Large eosinophilic
S100 +ve
CD68 +ve
Syringocystadenoma papilliferum
CYSTIC neoplasm opening into surface
Epidermis has hyperplasia and papillomatosis
Tumour shows papillary growth pattern with papillae composed of FIBROVASCULAR CORE surrounded by 2 layers of cells — inner tall columnar cells with eosinophilic cytoplasm
Plasma cells conspicuous
Look for associated sebaceous naevus
DDx: hydrocystadenoma, hydradenoma, hidradenoma papilliferum,
Granuloma annulare
Closed off palisading granulomas Upper third epidermis Granulomatous inflammation Mucin stain positive (colloidal iron, alcian blue) Normal dermis visible Eosinophils Multinucleated giant cells
Acantholytic acanthoma
Papillomatosis, epidermal hyperplasia with overlying hyperkeratosis
Prominent acantholysis throughout epidermis
Mild superficial perivascular infiltrate
Acute generalised exanthematous pustulosis
Subcorneal or superficial intraepidermal neutrophilic pustules with admixed few acantholytic keratinocytes
Background spongiosis with neutrophilic exocytosis and scattered dyskeratotic cells
Papillary dermal oedema
Perivascular mixed inflammatory infiltrate
Dermatofibroma aka fibrous histiocytoma
- Epidermal hyperplasia with flattened rete ridges ,
- Basal induction - induction follicles and sebaceous glands
- Poorly circumscribed proliferation of spindled and/or epithelioid fibroblasts and histiocytes
- Multinucleated giant cells - touton like
- Xanthomatised histiocytes
- Cellular dermis with collagen entrapment more prominent at periphery
Pilomatricoma
- Multinodular tumour in dermis and/or subcutis composed of nests resembling those of the hair matrix with abrupt transition to central shadow cells
- calcifications and foreign body granulomatous response
- numerous mitotic figures
Sebaceous adenoma
Nodular sebaceous and basaloid proliferation
Broadly connected to epidermis
Predominance sebaceous glands
Minimal cytological atypia
Erosion overlying is commmon
More mature sebocytes over less differentiated blue cells
Lipidized cells
MMR gene mutations MSH2, MSH6, PMS2, MLH1
T/F viral cytopathic change going down hair follicles is more likely VZV than HSV
True
Palisaded encapsulated neuroma
Well circumscribed but non encapsulated
Usually cleft but no capsule
Spindled cells wavy nuclei
Mast cells present
Bullous arthropod bite reaction
Subepidermal bulla ,
eos predominate
Superficial and deep eosinophilic infiltrate
Cylindroma
Jig saw arrangements of basaloid islands
Two cell populations small basaloid cells periphery and larger pale cells centrally
Eosinophilic aggregates within nests and around nests forming stroma
What is a sunburn cell
Single or few apoptotic cells high up in epidermis
Consistent with a photodermatosis
Polymorphous light eruption
Variable epidermal spongiosis with dyskeratosis
Superficial and deep mixed inflammation (mostly lymphocytic)
Red cell extravasation
Marked papillary dermal oedema
Chronic cutaneous lupus erythematosus
Follicular plugging
BM thickening
Lichenoid reaction pattern - basal vacuolation and apoptotic keratinocytes
Superficial and deep lymphocytic infiltrate
Mucin interstitially
Lupus tumidus
Relative sparing of epidermis
Superficial and deep lymphocytic inflammation
Mucin deposition interstitially
Subacute cutaneous lupus erythematosus
CF. DLE - presence of more epidermal atrophy - epidermal atrophy Basement membrane thickening Mucin deposition Superficial and deep lymphocytic infiltrate with periappendegeal spread /peri-eccrine - Less hyperkeratosis - Less Basement membrane thickening - Less follicular plugging - Less inflammatory infiltration
Lesions with keratin horn
Seb K
AK
IEC
SCC
Lichen planopilaris
Usually 8 pilosebaceous follicles in each mm of biopsy
Thus 36 or more follicles normal in a 4mm scalp biopsy
- lichenoid band like infiltrate with interface changes involving follicular infundibulum, concentric lamellar fibroplasia
- interfollicular epidermis usually spared
- loss of sebaceous glands and follicles
- DIF nonspecific cytoid bodies positive for IgM
- fusion of hair follicles - in LPP not lupus
Traumatic neuroma
- Proliferation of small bundles of well delineated nerve fascicles in a fibrotic stroma
STAIN: S100 for Schwann cells
Blastomycosis like pyoderma
Hyperplasia
Neutrophils
No evidence fungal/hyphae/
Sebaceous adenoma
Sebaceous lobule like structures
Peripheral basaloid cells (germinative cells) not more than >50%
need DNA mismatch repair markers
Cf. Sebaceoma - more disorganised, do not always retain the architecture; sebaceous duct like structures more prominent in sebaceoma
Mixed tumour of the skin
Chondroid syringoma
Circumscribed nodule
Clear cut cartilage with bluish appearance
Myxochondroid change, looks like cells are sitting in lacunae
Elongated , curved atubular structures
Rounded ductal structures / sometimes cystic structures
Lichen sclerosus
Hyperkeratosis Epidermal atrophy Some lichenoid change Follicular plugging Homogenised collagen [papillary dermis Underlying band like infiltrate
Adamantinoid trichoblastoma
Small nests with peripheral palisade — clear cells in middle not sebaceous origin
Warty dyskeratoma
Solitary cup shaped focus with acantholysis and dyskeratosis
DDx:
Acantholytic acanthoma — no dyskeratosis
Old lesions of Grover’s - can be proliferative/atypical
Comedonal Darier
Palisaded encapsulated neuroma
Fascicular arrangement of Schwann cells- often separated by small clefts with neural/wavy nuclei with pointed polar ends
- no dysplasia
- can see some nuclear palisading
- often has artefactual change like BCC where tumour separates from dermis
- no clear capsule or thin capsule only
s100 positivity
Ddx: NF, Pilar leiomyomas
Verruca (deep plantar wart)
Church spire like hyperkeratosis
See inclusion like keratohyalin
Diameter of microscope field Olympus microscope
11mm at x2 power
Secondary syphilis
Numerous plasma cells, superficial and deep
Lichenoid reaction pattern or psoriasiform reaction pattern with long thin rete
Endothelial cell swelling
Halo naevus
Regression in naevus
Lichenoid reaction centrally
Dense admixed lymphocytes in the upper dermis
Venous lake
Large dilated channel containing erythrocytes with thin endothelial lining with thin fibrosis
Dilated capillary/venule
Can be thrombosed secondary to trauma
Thrombophlebitis
Thrombosis within a thick walled lumen within the subcutaneous fat
Ddx: erythema induratum
Polyarteritis nodosa
Clear cell acanthoma
Well demarcated acanthotic epidermis with pale/clear cells, overlying parakeratosis and may co-exist with a prurigo nodule
—> PAS, followed by PAS-diastase to remove glycogen
Blue naevus
- Dendritic melanophages and spindled melanocytes
- Spindled cell proliferation, spindled melanocytes look like angulated cells with processes
- Often arranged around a follicular structure
- Pigment throughout lesion
Spitz naevus
Plump epithelioid nests
Vertical orientation of nests in papillary dermis
Doesn’t always have Kamino bodies
Juvenile xanthogranuloma
Sheet like nodular aggregates of lymphocytes histiocytes and eosinophils with admixed touton giant cells
- admixed xanthomatous cells / foam change
Syringoma
- Tadpole shaped eccrine structures in dermis forming tadpole-like structures
Phototoxic drug eruption
Intraepidermal blister with neutrophils
Epidermal necrosis
Pyogenic granuloma
Exophytic vascular nodule
Lobulated capillary network
Epidermal collarette
Neutrophils correlate with degree of ulceration
Polymorphic eruption of pregnancy
Nonspecific findings
— eosinophils with lymphocytic inflammation
— perivascular
— dermal oedema
Sebaceoma
Nodular sebaceous and basaloid proliferation
Nodular melanoma
- Prominent vertical growth phase
- few mitotic figures
- check peripheries in case arising in melanoma in situ
Ashy dermatosis
Lichenoid reaction pattern
Pigment incontinence
Upper dermal inflammation (lymphocytes/eosinophils)
Angioleiomyoma
- ## Discrete nodule in dermis of smooth muscle spindle cells arranged into fascicles
Lichen striatus
Combination of 2 reaction pattern in epidermis - spongiosis and lichenoid
— peri-eccrine lymphocytic infiltration
Clear cell hidradenoma
- solid and cystic areas with scattered ducts
DDx. poro-hidradenoma , many poroid cells
Mastocytosis
— Increase in mast cells
— look at proportion of mast cells to lymphocytes
Cellular Dermatofibroma
DF - CD13a positive, CD34 neg
Vs. DFSP - CD34 positive, CD 13a neg
Erythrasma
Corynebacterium - gram pos bacilli in s. Corneum
Pagetoid dyskeratosis
Urticaria
Neuts in vessel wall
Dermal oedema
Polymorphous infiltrate
Epidermolytic acanthoma
Hyperkeratosis
Slightly endophytic
Coarse granules
VACUOLATED cytoplasm with eosinophilic globules
Granulomatous pigmented purpuric dermatosis
Granulomas in upper papillary dermis
Haemosiderin deposition
Papillary dermis filled with lymphocytes and histiocytes
Hypertrophic lichen planus
Lichenoid reaction in rete ridges
Extramammary Paget’s disease
Intraepidermal proliferation with predominantly single cells with admixed nests throughout the epidermis
- individual cells are large with amphophilic cytoplasm, large nucleus and prominent nucleoli
CK7, CEA, Cam5.2, S100 - likely primary EMPD
- CK20, CEA, CAM5.2 positive, CK7, S100
CK20 positive == urothelial origin
VZV blister
More likely to have associated folliculitis
Warty dyskeratoma
Cup shaped invagination with overlying hyperkeratosis and parakeratosis
- acantholytic dyskeratosis of the invaginating epidermis with scattered corp ronds and grains is noted
- dermal papillae lined by basal cells resemble villi and project into the invagination
Glomus tumour
Solid, well circumscribed nodular proliferation of small monotonous cells with round central nucleus and eosinophilic cytoplasm around dilated blood vessels
- no atypic
- cell positive for SMA
Actinic keratosis
Variable keratinocytic atypia in lower layers of epidermis with overlying focal parakeratosis
- alternating ortho and parakeratosis
- “sail sign”
Lichen striatus
Lichenoid reaction pattern
Mixed spongiotic reaction pattern with lichenoid
- peri eccrine distribution
Sarcoidosis
Non caseating epithelioid granulomas in dermis and /or subcutaneous tissue with minimal lymphocytic infiltrate
- Schumann bodies or asteroid bodies present
Alopecia areata
Decreased anagen/telogen ratio (INCREASED TELOGEN HAIRS)
MORE CATAGEN HAIRS (AT LEAST 50% — R. MORTIMORE)
- sparse lymphocytic infiltrate around hair bulbs (swarm of bees) with admixed eos
- fibrous tracts seen with pigment incontinence +/- pigment casts
Traumatic fat necrosis
Lobular panniculitis
Fat necrosis , suppurative and granulomatous response
Erythema elevatum diutinum
NODULAR DENSE MIXED INFILTRATE WITH PREDOMINANT NEUTROPHILS AND LYMPHOCYTES, PLASMA CELLS, LCV. Fibrosis and lipid deposits in late lesions. May or may not have grenz zone
Trichotillomania
Peripilar haemorrhage Trichomalacia Pigment casts Lymphocytic infiltrate Increased catagen hairs
FOLLICULITIS DE CALVANS
Dense infiltrate of neutrophils and plasma cells surrounding ruptured follicular units
- follicular plugging and intra/perifollicular neutrophilic infiltrates
- neutrophilic abscesses and hair shaft granulomas in dermis with admixed lymphocytes, histiocytes
Acne keloidalis nuchae
Perifollicular lymphoplasmacytic infiltrate with neuts
- follicle rupture, hair shaft granulomas assoc. with suppurative inflammation and dermal fibrosis
Sinus tracts common
Deep penetrating naevus
Symmetric compound melanocytic proliferation , extends to lower reticular dermis and SC fat in wedge shaped pattern .
Nuclei small with hyperchromasia
—> extend down adnexae
—> stains with cyclin D1 - has had mutation in common with melanoma pathway
Desmoplastic trichoepithelioma
Cords and strands forming dermal proliferation ,
Angiomyxoid stroma
Dystrophic calcification
Microcystic adnexal carcinoma
- narrow, deeper islands with ductal differentiation
- stratified growth pattern with microcyst in upper portion and smaller nests and single cells at base
- invasion deep into subcutis (less likely syringoma)
- when around eye, have more prominent hyalinised stroma
- aka sclerosing sweat duct carcinoma
Polyclonal CEA stain - around eccrine ducts
Spindle cell SCC
- composed of partially or predominantly Atypical spindled cells in whorls or intersecting fascicles
- prominent mitoses
Angiokeratoma
Intermixed dilated vessels with acanthotic epidermis
Hyperkeratosis
Pseudoxanthoma elasticum
Wavy shortened elastic fibres in dermis
Stain: VVG, von kossa for calcium
Pseudo-PXE induced by penicillamine does not have calcium
Chondrodermatitis nodularis helicus
- narrow ulceration
- fibrin and necrosis above level of cartilage
- surrounding acanthosis
Granulation tissue, fibrosis in dermis below the ulceration - sometimes transepidermal elimination of cartilage
- cartilage if seen - can show degenerative changes
Morphoea profunda
Sclerotic collagen diffusely
Extending down to SC fat - septal panniculitis
Eccrine glands high riding
Loss of peri-eccrine fat
Collagenous and Elastotic marginal papules and plaques of the hand
- ## Thickened, vertically oriented collagen bundles with foci of calcification
Stains for sebaceous neoplasm
Adipophilin, EMA, MSH2, MSH6, MSH1, PMS2,
Lesions with pagetoid spread
Melanoma Merkel cell ca IEC SCC AK EMPD
Amyloidosis
Melanophages
Globular deposits of eosinophilic material with clefting
STAINS: crystal violet aka methyl violet - changes to magenta (metachromatic stain), Congo red, thioflavin T
Pityriasis versicolor
Distinct cell wall rather than artefact with poor edges
Spores and hyphae
PAS+
Does not enter the epidermis, only the stratum corneum
Photoaggravated drug eruption
- Dendritic cells in the dermis
- mild spongiosis due to acute on chronic reaction
- sunburn cells in the epidermis
Granular cell tumour
Can have malignant subtype
- proliferation of large to round polygonal cells with granular eosinophilic cytoplasm in sheets
- individual cells show indistinct borders, small round centrally located nuclei
- large eosinophilic cytoplasmic granules —> pustulo-ovoid bodies of Milan, positive
Stains: s100 positive, Cal-ritinene positive
Malignant subtype has Ki67
Pyogenic granuloma
- Significant cellularity around the vessels
- lobulated collection of dilated capillaries
Trichilemmoma
Endophytic proliferation of lobules with clear squamous cells
Angiosarcoma
Poorly demarcated proliferation of anatomising blood vessels (cracked collagen pattern) - and solid areas. Vessels show atypical spindled or epithelioid endothelial cells with multilayering and papillary structures - solid areas show sheets of spindled cells
EMPD STAINS
CEA, EMA, CK7
- mucicarmine
- CAM5.2
- CK20, GCDFP-15
PROGNOSTIC FEATURES OF SCC
- distance from tumour margin
- PNI
- LVI
- Clark level
- diameter >2mm
- site
Depth 2mm - recurrence
Syringocystadenoma papilliferum
Cystic neoplasm opening onto surface. Epidermis shows hyperplasia and papillomatosis. Double cell wall layer
Trichoepithelioma
CD34 positive stroma
Mesenchymal papillary body
Eccrine spiradenoma
Basophilic circular populations with eosinophilic aggregates, two cell population, lymphocytes percolating through nests
Pigmented spindle cell naevus of Reed
Junctional or compound (usually limited to papillary dermis) plaque like growth pattern with spindled melanocytes running parallel to epidermis
- conspicuous melanin pigment
- symmetrical configuration with sharp lateral borders no significant nuclear atypia
Stains for sebaceous neoplasm
Adipophilin, EMA, MSH2, MSH6, MSH1, PMS2,
Lesions with pagetoid spread
Melanoma Merkel cell ca IEC SCC AK EMPD
Amyloidosis
Melanophages
Globular deposits of eosinophilic material with clefting
STAINS: crystal violet aka methyl violet - changes to magenta (metachromatic stain), Congo red, thioflavin T
Pityriasis versicolor
Distinct cell wall rather than artefact with poor edges
Spores and hyphae
PAS+
Does not enter the epidermis, only the stratum corneum
Photoaggravated drug eruption
- Dendritic cells in the dermis
- mild spongiosis due to acute on chronic reaction
- sunburn cells in the epidermis
Granular cell tumour
Can have malignant subtype
- proliferation of large to round polygonal cells with granular eosinophilic cytoplasm in sheets
- individual cells show indistinct borders, small round centrally located nuclei
- large eosinophilic cytoplasmic granules —> pustulo-ovoid bodies of Milan, positive
Stains: s100 positive, Cal-ritinene positive
Malignant subtype has Ki67
Pyogenic granuloma
- Significant cellularity around the vessels
- lobulated collection of dilated capillaries
Trichilemmoma
Endophytic proliferation of lobules with clear squamous cells
Angiosarcoma
Poorly demarcated proliferation of anatomising blood vessels (cracked collagen pattern) - and solid areas. Vessels show atypical spindled or epithelioid endothelial cells with multilayering and papillary structures - solid areas show sheets of spindled cells
EMPD STAINS
CEA, EMA, CK7
- mucicarmine
- CAM5.2
- CK20, GCDFP-15
PROGNOSTIC FEATURES OF SCC
- distance from tumour margin
- PNI
- LVI
- Clark level
- diameter >2mm
- site
Depth 2mm - recurrence
Syringocystadenoma papilliferum
Cystic neoplasm opening onto surface. Epidermis shows hyperplasia and papillomatosis. Double cell wall layer
Trichoepithelioma
CD34 positive stroma
Mesenchymal papillary body
Eccrine spiradenoma
Basophilic circular populations with eosinophilic aggregates, two cell population, lymphocytes percolating through nests
Pigmented spindle cell naevus of Reed
Junctional or compound (usually limited to papillary dermis) plaque like growth pattern with spindled melanocytes running parallel to epidermis
- conspicuous melanin pigment
- symmetrical configuration with sharp lateral borders no significant nuclear atypia
Sweet syndrome
Epidermis normal
Marked papillary Dermal oedema
Florid neutrophilic inflammatory infiltrate with karyorrhexis
- true vasculitis can present focally
— Gossamer strands
DDx: pustular vasculitis
Rheumatoid neutrophilic dermatosis, BADAS, Behcet’s
Sebaceoma
Nodular Basaloid nests with sebaceous differentiation
Minimal cytologic atypia
Basaloid cells predominant >50%
STAINS: MSH2, MSH6, PMS2, MLH1 , adipophilin
Digital myxoid cyst
Localised deposit of mucin in cystic space
Cyst without any specific lining
— mucin stains: colloidal iron , alcian blue
Porokeratosis
normal basket-weave stratum corneum
No neutrophils
Vertical column of parakeratosis - cornoid lamella
Underlying hypogranulosis, focal thinning of epidermis with scattered dyskeratotic cells
Desmoplastic trichoepithelioma
Well demarcated discrete dermal lesion
Narrow cords and strands of compact epithelial cells and keratinous microcyst in a background of dense and collagenous sclerotic stroma
- BCC has high + staining for BCl-2
- BCl-2 also good for differentiating between inflamed Seb K and SCC (more positive in inflamed SebK)
- TE is positive for CK20 whilst a BCC is negative for CK20
Blue naevus
pigmented spindle cell proliferation
Dendritic melanophages in setting of sclerotic stroma
Lentigo maligna melanoma
Proliferation of atypical melanocytes at DEJ as confluent proliferation of single cells and nests
- extends along adnexal structures
- pagetoid spread within epidermis throughout the lesion
- eosinophilic stroma displaces solar elastosis
Bullous pemphigoid
Subepidermal cellular bullae —.eosinophils, neutrophils , lymphocytes
DDx: EBA, bullous arthropod bite reaction, bullous drug
Cf.
EBA - 1. vesiculation can involve adnexae unlike BP
2. More neutrophils
Keratoacanthoma
- Large glassy keratinocytes forming sheets
- Associated with pseudohorn cysts
- Chronic inflammation and scarring
- associated with multilayering of sweat ducts - syringometaplasia
Neurofibroma
Variably circumscribed, non encapsulated proliferation of spindle cells with wavy nuclei, arranged haphazardly in a loose myxoid stroma
Scattered mast cells
Stains: s100 for Schwann cells positive, tryptase for mast cells m CD34 positive stroma
Inverted follicular keratosis
Endophytic proliferation of squamous epithelium and basaloid cells with finger like projections into the dermis
Squamous eddies characteristically present at base
Mild lymphohistiocytic infiltrate in dermis
Trichofolliculoma
Large central primary dilated follicular infundibulum with multiple small secondary hair follicles emptying into mother follicle
- cellular fibrous stroma in close approximation to the hair follicle
Schwannoma
Encapsulated lesion in dermis and/or subcutis
Cellular areas composed of closely packed spindle cells with tapered wavy nuclei
- producing a palisading pattern (Antoni A)
Intermixed less cellular areas showing scattered spindle cells
No neurofilament - no axons
Positive neurofibromin
Apocrine hydrocystoma
Unilocular or multilocular cystic cavity lined by TWO layers of epithelial cells with decapitate secretions in lumen
Dermatofibroma
Basal induction Acanthotic and hyperpigmented basal layer Spindled cell proliferation papillary mesenchymal bodies Sclerotic entrapment of collagen
Mixed tumour of the skin
Well circumscribed biphasic tumour with admixed epithelial and mesenchymal components
Plasmacytoid
Dyscohesive solid masses of cells - myoepithelial cells
Atypical genital naevus
Large atypical junctional nests
- Stromal fibrosis/lamellar fibrosis
- can be confused with melanoma
PITYRIASIS VERSICOLOR
Spores and hyphae in stratum corneum
- COMPARED TO DERMATOPHYTE INFECTION
—> LESS SPONGIOTIC
—> NO NEUTROPHILS
—> no sandwich sign
Atrophic epidermis only ~3 cells thick with lichenoid ddx
Dermatomyositis
Lupus
Porokeratosis
Trichoadenoma
Small doughnut like proliferation of keratolytics composed of eosinphilic squamous cells with large central horn cysts. Fibroblastic stroma
Epidermal type keratinisation with granular layer
HSV folliculitis
- Sebaceous gland necrosis
- Neutrophilic debris
Digital myxoid cyst
Localised deposit of mucin in cystic space
- cyst without specific lining
Interface obscuring lichenoid dermatitis
Erythema multiforme (reticulated degenerative changes in late biopsy)
SJS/TEN
FDE (pigment incontinence, neutrophils in infiltrate)
PLEVA (parakeratosis, erythrocyte extravasation)
SCLE (follicular involvement, BM thickening, mucin)
GVHD
Adjacent herpes blister
paraneoplastic pemphigus (suprabasal acantholysis)
Acute lupus erythematosus
Desmoplastic melanoma
SUBTLE proliferation of spindle cells in dermis with scattered atypical cells
- spindle cells may form fascicles in a fibrotic stroma
Perineural invasion often seen
S100 best, SOX-10 good too
HMB-45 , Melan-A can often be negative
Fibroepithelioma of pinkus
Anastomosing thin strands of epidermis with fenestrated appearance
In setting of fibroblastic stroma
Flegel disease
Hyperkeratosis with focal parakeratosis / papule has a discrete zone of ortho-hyperkeratosis contrast with normal epithelium
- in the periphery the epidermis is acanthotic with colarette-like elongated rete ridges,
- lymphocytic lichenoid infiltrate in early lesions
- EM membrane coated granules (Odland bodies)
- slight degree of hyperchromatic mood or nuclear infoldings - resembling Sezary cells, have been described in some cases of Flegel disease
Schwannoma
Circumscribed encapsulated dermal nodule
Antoni A and B areas
Palisaded nuclei
Thickened vessel walls
Vitiligo
Absence of melanocytes (halo cells)
Sparse inflammatory infiltrate
Epidermal atrophy
\STAINS: SOX-10, Melan-A, HMB-45, s100
Discoid eczema
Stratum corneum serum crust Spongiosis of epidermis Epidermotropism of lymphocytes Eosinophils Drug induced spongiotic dermatitis - pityrisiaform spongiosis according to KC Chong
HSV infection
Margination of chromatin
Steel gray nuclei
Nuclear dust
Intraepidermal vesicles - mixed inflammatory infiltrate: variable in HSV infection according to KC Chong (can have neuts, eos, or be monomorphic)
Actinic keratosis
Parakeratotic changes in stratum corneum - compact hyperkeratosis, nuclear dysplasia
Sometimes acantholysis
Pigmented spindle cell naevus of Reed
Spindled melanocytes run parallel to the epidermis
Junctional or compound plaque like growth pattern
Symmetrical configuration with sharp lateral borders
Younger patient — no solar elastosis
Mycosis fungoides
Atypical lymphocytes giving rise to Pautrier microabscesses
Exocytosis of lymphocytes/epidermotropism (more atypical and larger than lymphocytes in the dermis)
Wiry collagen fibres
Single lymphocytes lining up against the Basement membrane zone
Atypical lymphocytes are surrounded by halos
Mixed tumour of the skin/choroid syringoma
Circumscribed dermal nodule with two cell populations
Fibromyxoid stroma
Mastocytosis
Cf normal mast cells
—> in mastocytosis, hypertrophic and clustered, more spindled
—> stains: tryptase is the most specific - CD117, toluidine blue (metachromatic change blue to purple)
Trichilemmoma
- Eosinophilic lobules with eyeliner sign - palisaded - has some incr pink cuticle/basement membrane surrounding lobules
- clear cells centrally
- can have scattered mitoses
DDx: clear cell IEC, clear cell SCC, clear cell acanthoma, sebaceous differentiation
Inverted follicular keratoma
Endophytic , somewhat bulbous, lobular proliferation with squamous eddies
- keratinocyte proliferation seems to surround one or several follicular canals opening onto the surface
Tumour of follicular infundibulum
Fenestrated and plate like structures
- pale pink cells
Melanoma in situ
- superficial spreading
Symmetry/poor peripheral circumscription (but cannot comment on this on a partial biopsy specimen)/pagetoid/
Nested though Scatter of single cells throughout all levels of epidermis
Mitoses
Variable stromal reaction
Fibrosis within the dermis
Scatter of cells above basal layer
Angiofibroma /fibrous papule of the nose
Concentric fibrosis around follicle
Angioma OPD stroma
Fibroblasts - can be multinucleated
Superficial multifocal BCC
need to Comment on regression or evidence of tumour beyond scar
IEC
Comment on solar elastosis, whether has an underlying epidermal lesion eg. Actinic keratosis
- look for dermal invasion
-
Hydrocystoma
- apocrine snouting
- Unilocular
Blue naevus
- common sclerotic
Spindled dendritic melanocytes in dermis
Melanophages - histiocytes containing excess melanin pigment
Thickened collagen associated with lesion
Neurofibroma
Spindle cell proliferation in dermis with wavy nuclei
Loose stroma with fibrillary architecture
Mast cells
No cytological atypia
Neurofibrosarcoma only really seen in context of neurofibromatosis
Porphyria cutanea tarda
Caterpillar bodies - PAS positive
Dermal festooning
Paucicellular subepidermal blister
Granuloma annulare
Closed off granulomas with necrobiosis
- Mucin, presence of eosinophils , less likely plasma cells
- perivascular lymphocytes
Usually upper portion of dermis (upper 1/3)
- areas of dermal dermis also present
- multinucleated giant cells
Proliferating trichilemmal cyst
Abrupt keratinisation
—> transition to keratin
- can have cytological atypia
Akermann considered this a form of SCC
Lichen sclerosus /balanitis xerotica obliteraans
Homogenisation of collagen in papillary dermis
Can have eosinophils
Can see smooth muscle and nerves in specimen of this area
Mucocoele
Myxoid stroma
Pseudo cystic structure containing mucin
Glandular structures on lip
Warty dyskeratoma
;Cup shaped invagination with acantholysis
- acantholytic dyskeratotis at the base and sides of a cup like epidermal invagination
Flattened parakeratosis = grains
Shrunken nuclear bodies with perinuclear halo
Eccrine poroma
Monomorphous cell population
individual cells trying to form a duct
Connecting to epidermis
Raining down(classic)
MF stains
CD2 - rarely lost
CD5 , 2 — both reliable T cell markers
CD4 , 8 — for clonality
CD30 — exclude LyP, ALCL
Deep penetrating naevus
B-catenin positive
Extend down adnexal structures
Clonal naevus
Small discrete nests of large pigmented epithelioid melanocytes
DARIER VS. GROVER DISEASE
Both have acantholytic dyskeratosis
DARIER = more serum crust , more inflammation
GROVER = less serum crust, less inflammation
PLEVA
Parakeratosis, lymphocytic vasculitis, erythrocytes extravasation, Vacuolar damage, apoptotic keratinocytes
Dermal oedema seen in?
Sweet syndrome Id reaction Urticaria PMLE Arthropod bite Phytodermatitis Perivascular oedema in perniosis
Acral fibrokeratoma
Thick collagen bundles surrounded by bloods vessels, oriented perpendicular to the epidermis
DDx: ungal fibroma, supernumerary digit
Desmoplastic melanoma
pauciceullar atypical Spindled cell proliferation - atypical, spindled, malignant melanocytes
- separated by fibrocollagenous stroma within the dermis or SC fat
- often overlying melanoma in-situ, typically of LM type
Areas that look like nerve
Lymphocytic aggregates
Do not stain positive for HMB-45 or Melan-A,
Can stain + for PRAME IHC stain
Kaposi sarcoma
Haemosiderin and plasma cells at edges
Can have Polypoid appearance
Slit like spaces
Angiosarcoma stains
ERG
C-MYC
ALOPECIA AREATA
Terminal to vellus hair ratio 1:1
Prominent sebaceous glands
Fibrous streamers and miniaturisation can be seen
Swarm of bees lymphocytic inflammation
Can see pigmented casts
Large numbers of catagen and telogen hairs
Granular parakeratosis
Retained keratohyalin granules
Can have epidermal necrosis and exocytosis of neutrophils
Idiopathic scrotal calcinosis
Amorphous basophilic granular material
Giant cell granulomatous reaction at edges
Dermato fibrosarcoma protuberans
Storiform configuration of spindled cells
Depth of involvement with honey combing
Fairly monomorphous cytology although invasive
- CD34
- Factor VIII
Interface obscuring lichenoid reaction pattern
EM PLEVA Fixed drug eruption SJS / TEN LE
What can shadow keratinisation/cells be found in:
Pilomatricoma
Pilomatricarcinoma
BCC
Follicular adnexal neoplasms
Sarcoidal granulomas can be seen in:
FIGS RC Sarcoidosis Infections Foreign body granulomatous reaction pattern Granuloma annulare Rosacea Cutaneous Crohn’s disease
Endophytic squamous proliferation - as a term rather than pseudoepitheliomatous hyperplasia
Favour reactive aetiology
Sporothrix
—> can resemble asteroid body
Suppurative granuloma
- Contains abundant neutrophils
- subtle granulomas
Gout
Fibrillar/Shieves of wheat appearance
Can ask to process in alcohol so crystals do not dissolve
Gout vs. pseudogout —> basophilic look to pseudogout as more calcified, gout with more pointy ends (soft sign)
Perifollicular granulomatous reaction pattern
- ruptured folliculitis
—> can see flakes of keratin
—> can see some necrosis though slightly unusual in folliculitis (see this in acne necrotica) - annular elastolytic giant cell granuloma
Chalazion
Prominent plasma cells
Granulomatous reaction pattern
Intravascular papillary endothelial hyperplasia / Masson’s tumour
Reactive proliferation of endothelial cells with papillary formations related to a thrombus
- can be mistaken for angiosarcoma
Pityriasis rosea
Mild spongiosis and focal parakeratotic mounds
Superficial perivascular lymphocytic infiltrate with extravasated RBC, sometimes admixed eos
- DDx: EAC
Keratoacanthoma
Crateriform architecture with glassy eosinophilic atypia, Neutrophilic microabscesses, eosinophils and elastic trapping - acantholysis never present PNI can be present Lymphovascular invasion unlikely SCC can be present in the base of KA
Angiokeratoma
Acanthotic epidermis with hyperkeratosis
Intermixed dilated vessels surrounded by epidermis giving appearance of intraepidermal vessels
Tumour of follicular infundibulum
Superficial distinct plate-like epithelial proliferation
MULTIPLE connections to epidermis - slender epidermal connections with basaloid or pale cells
Less hyperkeratosis than SebK
Lichenoid keratosis
Lichenoid infiltrate composed primarily of lymphocytes with scattered histiocytes
- eosinophils and plasma cells are sometimes present
- see basal vacuolation, colloid bodies and melanin incontinence
Epidermolytic acanthoma
FOUR COMPONENTS IN THIS HISTOLOGIC PATTERN:
1 - clear spaces of varying size surrounding nuclei in the stratum spinosum and stratum granulosum . Large cytoplasmic vacuolation of cells above basal layer with indistinct cell borders
2 - indistinct cellular boundaries consisting of reticulated, lightly staining material
3 - a markedly thickened granular zone containing an incr number of small and large, irregularly shaped, basophilic keratohyalin-like bodies
4 - compact hyperkeratosis
The basal layer is normal. Epidermolytic acanthomas generally demonstrate more papillomatosis than seen in other conditions with EHK.
Angioleiomyoma
Well circumscribed, subcutaneous or dep dermal nodule. Large interfacing bundles of plump spindle cells with ample eosinophilic cytoplasm, cigar-shaped nuclei and paranuclear vacuoles arranged around slit like
Calcification very uncommon - can happen on acral sites
Dermatofibrosarcoma protuberans
- Dermal and SC proliferation of spindle cells in distinct storieform pattern; spindle cells are uniform with minimal atypia.
- Involvement of subcutis imports a layered and honeycomb pattern.
- No epidermal induction
- Not necessarily extending to fat
- CD34 stain positive
- factor XIIa negative (unlike dermatofibroma)
Morphoea
Dermal sclerosis with thick closely packed hyalinised collagen bundles. Loss of periadnexal fat, atrophy of adnexal structures, especially pilosebaceous units. Blood vessels appear narrowed with thickened walls. Sparse lymphoplasmacytic infiltrate.
Chondroid syringoma
Benign tumour of sweat glands with a mucoid stroma showing cartilaginous metaplasia
- chondromyxoid stroma
Can be apocrine or eccrine
Clonal naevus
Conventional compound naevus and naevus with large epithelioid melanocytes
- similar to deep penetrating naevus which has mutation in beta-catenin gene (but clonal naevus does not have mutation)
Lichen striatus
Focal parakeratosis Mild acanthosis, sometimes psoriasiform Spongiosis Dyskeratotic keratinocytes sometimes Focal basal layer liquefaction sometimes Perivascular or lichenoid lymphocytes , often around follicles and ESPECIALLY AROUND SWEAT DUCTS (syringocentricity)
Microcystic adnexal carcinoma
Infiltrative , poorly circumscribed eccrine neoplasm with focal Pilar differentiation
- stratified growth pattern with microcyst in upper portion and small nests and single cells at the base
- SUPERFICIAL: more squamous
- INTERMEDIATE: Strands and small nests
- DEEP: Cystic
- nests of squamoid cells with minimal cytological atypia and duct form
Traumatic neuroma
Proliferation of small bundles of well delineated nerve fascicles in a fibrotic stroma
Angiosarcoma
Proliferation of Vessels surrounded by Enlarged endothelial cells
Surrounded by inflammatory infiltrates
CD31, CD34
Perniosis
Superficial and deep lymphocytic
Fluffy perivascular oedema
Eccrine (peri eccrine) inflammation
Desmoplastic melanoma
Often little in situ component
Spindled cell proliferation
Lymphoid aggregates at the edges
Acral compound naevus
Larger irregularly shaped pigmented junctional nests
Sometimes pagetoid spread
Predominance of nests over lentiginous pattern
A lack of confluent lentiginous component
Usually well circumscribed and asymmetrical
Usually not inflamed
Inverted follicular keratoma
Endophytic proliferation of squamous epithelium and basaloid cells with finger like projections into the dermis. Squamous eddies characteristically present, particularly at the base. Mild lymphohistiocytic infiltrate in dermis
Dilated pore of winer
Keratin plugged dilated follicular infundibulum with small radiating epithelial projections
Dilated pore of winer
Keratin plugged dilated follicular infundibulum with small radiating epithelial projections
Granular cell tumours
Proliferation of large round to polygonal cells with granular eosinphilic cytoplasm in sheets Necrosis Pleomorphism Mitoses Perineural activity No invasion
Chronic radiation dermatitis
Hyperkeratosis with epidermal atrophy
Hyalinised stroma and oedema of papillary dermis
Hyalinised vessel walls and intimate hyperplasia
Large stellate radiation fibroblasts with atypical changes
Loss of adnexa
Proliferating trichilemmal cyst
Multilobulated tumour composed of lobules of squamous epithelium showing abrupt trichilemmal keratinisation. Peripheral palisading and thickened BM ma be noted. Focal keratinisation with squamous edges.
Merkel cell carcinoma stains
CK20, CK7
chromogranin A
Synaptophysin
CD31 -for extension to lymph node /lymphatic invasion
Negative:
- s100,
- Common leukocyte antigen
- TTF1 (small cell lung ca less likely to form sheets and trabeculae)
Chronic cutaneous lupus erythematosus
- BM thickening
- Epidermal atrophy
- Follicular plugging
- Mucin DEPOSITION
- Superficial and deep lymphocytic inflammation, periappendageal and peri-eccrine
Glomus tumour
Proliferation of rounded, homogeneous, hyperchromatic glomus cells surrounding vascular lumina
Positive smooth muscle active
Negative CD31, 34
Calcinosis cutis
Deeply basophilic brittle deposits in the dermis
Occasionally surrounded by foreign body reaction
Positive for von kossa and alizarin red
Trichoadenoma
Multiple small doughnut like proliferation of keratolysis composed of eosinophilic squamous cells with large central horn cysts
- epidermal type keratinisation with granular layer
- fibroblastic stroma
Large cell acanthoma
Acanthotic epidermis with cells showing large nuclei, almost twice the size of normal keratinocytes.
Occasional verrucous pattern with papillomatosis or hyperkeratotic pattern may be seen.
Stain for naevus vs. melanoma
P16 - positive in naevi
Negative in melanoma
Hailey hailey disease
Extensive acantholysis usually at mid epidermis resembling dilapidated brick wall. Follicle sparing (unlike Darier)
Focal dyskeratosis (eosinphilic band surrounding nucleus)
Perivascular lymphocytes
DIF -
Atypical fibroxanthoma
- CD10, CD99
Can stain positive for SMA
Epithelial marker
P40 positive
In SCC
