Histopathology Flashcards
Difference between mucocutaneous pyoderma and DLE (aside from bacteria)
DLE has hydropic degeneration of basal cell layer AND interface band of inflammation
MCP has interface band of inflammation WITHOUT keratinocyte cytotoxicity!
Difference between interface cytotoxic dermatitis and panepidermal cytotoxic dermatitis
Interface: basal cell layer apoptosis only
Panepidermal: Multilayer apoptosis through epidermis
What category of diseases are cell-poor cytotoxic (interface) dermatitis
Chronic vasculopathies, Ischemic dermatopathy like dermatomyositis
2 causes for hydropic degeneration
Cell rich: CD8 T cells and NK cells mediate apoptotic cell death
Cell poor: hypoxia 2’ chronic vascular damage. Induces endoplasmic reticulum stress + autophagy
Where on the body are plasma cells present in cytotoxic interface dermatitis
Mucosal, mucocutaneous lesions
(otherwise, usually just lymphocytic +/- DCs, macrophages)
What are “sunburn cells”
Apoptotic keratinocytes 2’ UV damage. Usually in stratum spinosum. NO SATELLITOSIS w/T cells.
-CLE, photodermatoses
Which cytokine do Th1 CD4 T cells, CD8 T cells, ILC1, NK, NK-T cells produce
IFNg
Which cytokine is upregulated in dogs with CLE
IFNg
Which chemokine is upregulated in dogs with CLE
CXCL10 (made by T cells, keratinocytes)
Which diseases have confluences of apoptotic keratinocytes in the epidermis
SJS/TEN (but dermis is NORMAL)
Thermal burn (but dermis is ABNORMAL/ulcerated)
What causes thickening of the BMZ in DLE, MCLE, hyperkeratotic EM
Deposition of immunglobulins and immune complexes
What may cause dermal mucinosis in DLE
Keratinocytes upregulate versican 1 d/t IFNg stimulation
Cytotoxic panepidermal dermatitis with parakeratosis diseases [follicular infundibular epithelium severely affected + satellitosis] (4)
*Feline proliferative and necrotizing otitis externa
*Infiltrative mural folliculitis and dermatitis with apoptosis and parakeratosis (black labs)
*Hyperkeratotic EM
*Superficial necrolytic dermatitis
Acanthosis definition
Thickening of the stratum spinosum
Where are arrector pili muscles on the body
Dorsum
Animals with simple hair follicles
*Human
*Cattle
*Horse
*Pig
Animals with compound hair follicles
*Dog
*Cat
*Sheep
*Goat
Which animal has a thick connective tissue layer in the deep dermis
Horses
Where is skeletal muscle present in the skin?
Muzzle, forehead, eyelids, perianal region
Where is the stratum lucidum visible in dogs?
Pawpads
General causes for necrosis vs apoptosis
Apoptosis: immune-mediated
Necrosis: photosensitization, burn, TEN
Which protein and cells are implicated in TEN (full thickness epidermal necrosis)
Granulysin from CD8+ T cells and NK cells
Stain for mycobacteria
Acid fast, Fite
(short rods, filamentous)
Stain for Burkholderia
Warthin-Starry
Stain for oomyctes
GMS
IHC marker for epithelial cells
Cytokeratin
IHC marker for mesenchymal cells
Vimentin
IHC marker for T cells
CD3
IHC marker for B cells
CD20
PAX5
CD79a
IHC marker for histiocytes
Iba1
CD18
Where on the body is there minimal SC fat
Limbs
How to distinguish mucin from solar elastosis
Both are lightly basophilic areas in the upper dermis
Solar elastosis: can still see the thin fibers
Mucin: no fibers, more generalized, smudgy blue
Histopath for acral lick dermatitis
*Vertical dermal fibrosis, streaking
*Acanthosis
*Compact hyperkeratosis (ortho or parakeratotic)
Histopath for eosinophilic plaque
*Epidermal hyperplasia
*Spongiosis
*Exocytosis of eosinophils
*Perivascular eosinophilic dermatitis
Histopath of psoriasiform lichenoid dermatosis
*Psoriasiform epidermal hyperplasia
*Cocci in crust
2’ cyclosporine OR English Springer Spaniel w/Staph hypersensitivity
Which virus has intraNUCLEAR inclusion bodies
Herpes
Papilloma
(DNA viruses)
Which virus has intraCYTOPLASMIC inclusion bodies
Poxvirus
Disease in a goat with intracytoplasmic inclusion bodies
Poxvirus
Contagious ecthyma
“Orf”
Spontaneous regression in 1 month
Zoonotic
How can you differentiate sebaceous adenitits from Leishmania?
Sebaceous adenitis has granulomatous/pyogranulomatous sebaceous adenitis with NO nodular dermatitis. Negative IHC for Leishmania
Leishmania has NODULAR to DIFFUSE dermatitis in addition to the sebaceous gland involvement. + IHC for Leishmania spp.
Diseases where sebaceous glands are destroyed as secondary targets
*Sterile granuloma and pyogranuloma syndrome
*Juvenile sterile granulomatous dermatitis and lymphadenotitis
*Uveodermatologic syndrome
*Demodicosis
*Canine Leishmania
Idiopathic sebaceous adenitis (dogs, humans, cats, rabbits, horses) = cell-mediated destruction of sebaceous glands.
Breeds for sebaceous adenitis
*Standard poodle (autosomal recessive)
*Akita (autosomal recessive)
*Samoyed
*Vizsla
*Dachshund
Infundibular keratinizing acanthoma
Trichoblastoma
Inferior tricholemmoma
Pilomatricoma
Trichoepithelioma
Guinea pig
Trichofolliculoma
Follicular cyst
Dog. Crusted pawpad
Pemphigus foliaceus
Broad subcorneal pustules with acantholytic keratinocytes, well-preserved neutrophils +/- eosinophils
DSC1
Dog. Deep ulcers on mucosal surfaces
Pemphigus vulgaris
Vesicles, suprabasilary clefting with tombstoning of basal keratinocytes. Hemorrhage and serocellular exudate in the clefts. Usually, mucous membranes affected, but MAY involve hair follicles
DSG3
Type 2 hypersensitivity
Dog. Young. Ulcerate lesions on concave pinnae, oral cavity, footpads, nasal skin
Erosions and ulcers on axillae, abdomen, inguinum
Junctional Epidermolysis Bullosa
Laminin 332 –> split through the lamina lucida. Minimal to no inflammation
PAS on DERMAL side (stains lamina densa)
Ulcerated paw pads, pressure points
Dog. Well-demarcated, hyperkeratotic, alopecic plaques
Darier’s Disease
Suprabasilar clefting due to profound acantholysis. NO neutrophils. Acantholytic keratinocytes = corp ronds
Bernese Mountain dogs overrepresented??
ATPA2 gene, SERCA2 ATPase pump located in endoplasmic reticulum
Autosomal dominant
Young GSHP
Exfoliative cutaneous lupus erythematosus
Cell poor interface dermatitis AND sebaceous adenitis
Nearly identical histopath to feline thymoma-associated exfoliative dermatitis
1/3 have lymphadenomegaly. Many develop arthralgia. Infertile. A`nemia, fluctuating thrombocytopenia. (Variant of SLE?)
Dog. Erythematous macules, papules, plaques on haired skin, foot pads, pinnae, MM
Erythema multiforme
Lymphoplasmacytic interface dermatitis with transepidermal apoptosis, lymphocytic satellitosis
+/- erosions/ulcers
+/- parakeratosis
Idiopathic vs drug induced. Type 4 hypersensitivity targeting KCs.
Collie. Ulcers on ventral abdomen
Vesicular cutaneous lupus erythematosus
Lymphoplasmacytic interface dermatitis with apoptosis of basal keratinocytes. May have erosions/ulcers with vesicle formation
Collies, Shelties
Cat. Old age.
Thymoma-associated exfoliative dermatitis
Lymphoplasmacytic interface dermatitis with apoptosis of basal +/- spinous KCs. May affect follicular epithelium. NO SATELLITOSIS (differentiate from EM). LOSS OF SEBACEOUS GLANDS. Orthokeratotic hyperkeratosis
Exfoliation on head, neck, pinnae –> general.
Not always paraneoplastic. Can occur in rabbits, goats too!
MALASSEZIA YEAST OVERGROWTH ON CYTOLOGY
Dog. Onychomadesis
Symmetric lupoid onychodystrophy
Cell poor lymphoplasmacytic interface dermatitis. Pigmentary incontinence. Apoptosis of basal keratinocytes. D-E junction “unzipping”
- Histopath unlikely to be on boards
Dog. Middle-aged. Nasal planum.
Discoid lupus erythematosus
Lymphoplasmacytic lichenoid-interface dermatitis. Basal cell apoptosis. Pigmentary incontinence
Need clinical correlate to differentiate from mucocutaneous pyoderma
Pemphigus foliaceus
Stain to confirm AISBD?
PAS (can also do Collagen 4 IHC, or salt-split immunofluoresence)
Dog. Crusts, erosions/ulcers, on paw pads, pressure points, MC junctions
Hepatocutaneous Syndrome
Red = parakeratosis
White = laminar edema
Blue = basal cell hyperplasia
Liver: Honey comb on AUS. Hypoaminoacidemia, decreased serum essential fatty acid levels
Bird
Avian pox
Opaque, yellow papular lesions on head, MM
Epidermal hyperplasia with hydropic degeneration. Eosinophilic intracytoplasmic inclusion bodies (Bollinger bodies) in KCs.
Cat. Well-demarcated, raised, erythematous plaques on abdomen, thighs.
Eosinophilic plaques
Severe acanthosis with moderate spongiosis of epidermis, follicular epithelium. Accumulation of mucin. Perivascular to diffuse eosinophilic dermatiits
R/o FAD, CAFR, AD
Cat. Ulcerations on face, nasal planum
Feline Herpesviral Dermatitis
Ulcerative dermatitis. Intranuclear viral inclusions in KCs (within the ulcer) with severe eosinophilic dermatitis
FHV-1. Latency in Trigeminal ganglia.
Dog. Raised nodular mass on distal limb
Acral lick dermatitis
Erosion/ulceration with acanthosis and furunculosis. Free hair shafts embedded within pyogranulomatous dermatitis. Hyperplastic apocrine glands.
+/- bacterial folliculitis or on the surface (licking)
*Check for demodex or dermatophytes
Dog on cyclosporine.
Psoriasiform Lichenoid Dermatosis
1) Spontaneous in springer spaniels.
2) 2’ Cyclosporine in any breed
Staph hypersensitivity reaction pattern??
Lymphoplasmacytic lichenoid dermatitis with papillary epidermal hyperplasia, hyperkeratosis, Munro’s microabscess (neutrophilic pustule in epidermis), and cocci
Multifocal, well-circumscribed hyperkeratotic and alopecic papules, plaques. Concave pinnae
Disease with Munro’s microabscesses
Psoriasiform lichenoid dermatosis
(neutrophilic pustule)
Young Golden retriever
Ichthyosis- nonepidermolytic
Orthokeratotic hyperkeratosis; brightly eosinophilic, densely compacted keratin– tightly adherent
Golden retriever:
Type 1: PNPLA-1. Autosomal recessive
Type 2: ABHD5. Autosomal recessive. More severe.
2’ bacterial, malassezia infx
Young norfolk terrier
Epidermolytic ichthyosis
Acanthosis with prominent granular cell layer. Vacuolation, lysis of kerationcyte in granular/spinous layers. Orthokeratotic hyperkeratosis (not as compacted as non-epidermolytic ichthyosis)
Pigmented scale, hyperkertotic plaques in inguinum since birth
Norfolk Terrier. KRT10. Autosomal recessive
Vizsla
Sebaceous adenitis
Lymphoplasmacytic periadnexal dermatitis with loss of sebaceous glands. Orthokeratotic hyperkeratosis and follicular keratosis
Standard Poodle, Akita, Vizsla (nodular variant), Havanese
Husky
Zinc responsive dermatosis
Marked parakeratosis with acanthosis and patchy loss of granular cell layer. Parakertosis extends into follicular ostia. Spongiosis and perivascular to interstitial dermatitis
Breeds: Arctic dogs. NEW: Frenchies, Boston Terriers on pinnal margins!
Dog. Nasal planum
Proliferative Nasal Arteritis
Ulceration, fissuring. Thickened arterioles underneath ulcer bed. Marked thickening of tunica intima with spindle cells, mucinosis. +/- thrombi.
Saint Bernard, GSD
Akita
Uveodermatologic syndrome (VKH)
Histiocytic and lymphoplasmacytic LICHENOID inflammation w/ “fine dusting” of melanin within macrophage (pigmentary incontinence).
Depigmentation/ leukotrichia/ ulcers in Chow Chow, Akita, Malamutes, Husky, Samoyeds
Uveitis –> blindness
Boxer. Nodular mass on pinna
Canine Leproid Granuloma
Granulomatous to pyogranulomatous nodular dermatitis. Acid fast + bacteria in macrophages.
Difficult to culture. Enters skin 2’ trauma.
Pinna mass on boxer. Diagnosis?
Leproid granuloma
Negatively staining cytoplasm of macrophages
Non-tuberculous mycobacterium
(pic = PAS histo)
Diagnosis?
Leishmania
Leishmania has perpendicular kinetoplast
Trypanosoma has parallel kinetoplast
Dog or cat from TX
Leishmania
Pyogranulomatous inflammation. Parasitophorous vacuoles filled with Leishmania amastigotes. LOSS OF SEBACEOUS GLANDS
Giemsa stain
In the USA: Leishmania mexicana (cats) cause nodular swellings on the pinnae and face. Zoonotic. Natural host in TX = woodrats
Immunosuppressed dog or cat.
Gram +, Weakly acid fast
Nocardiosis
Pyogranulomatous dermatitis/cellulitis with rare colonies of branched filamentous bacteria. Gram +, weakly acid fast.
(Actinomyces is NOT acid fast)
PERSIAN Cat. SQ nodule on trunk, dorsal tail.
Dermatocytic pseudomycetoma
Pyogranulomatous nodular dermatitis with intralesional aggregates of non-pigmented fungal hyphae. +/- Splendore-Hoeppli phenomenon. Stains + with GMS, PAS
Microsporum canis. (Fungal kerion on face if this was a dog).
Pseudomycetoma = organism in tissue as grains, but NOT mycelial formation.
Cat. Bridge of nose
Cryptococcus
Granulomatous inflammation with “soap bubble” appearance– unstained, thick heterpolysaccharide capsule. Narrow-based budding
Clinical: Roman nose. Can occur in immunoCOMPETENT animals
Stain: Mayer’s mucicarmine (also PAS, GMS)
Horse or cat. Raised dermal nodules
Pheohyphomycosis
Pyogranulomatous inflammation with pigmented fungal hyphae.
Dermal, SC masses on face, distal extremities w/ draining tracts.
Stain = Fontana-Masson to highlight melanin in hyphae
Cats, Horses that are immunCOMPETENT. Dogs are immunosuppressed. GSD predisposed.
ABCCEO
A=Alternaria
B=Bipolaris
C=Cladosporium
C=Curvularia
E=Exophiala
O=Ochroconis
Horse
Habronemiasis, “Summer Sores”
Nodular to diffuse, granulomatous/ eosinophilic dermatitis with erosion, ulceration. 50% have Habronema larva
Firm, proliferative nodular lesions w/yellow debris. Periocular.
Habronema muscae, Habronema majus, Draschia megastoma
(Vector = stable fly, house fly)
Opaque, white nodules on cat
Xanthomatosis
Nodular to diffuse foamy extracellular lipid lakes, acicular cholesterol clefts, granulomatous inflammation, multinucleated giant cells (Touton’s type)
Abnormal lipid metabolism, high fat diet, Diabetes mellitus, hypothyroidism.
Cat pawpad
Plasma cell pododermatitis, nasal dermatitis
Dense sheets of plasma cells, variable Mott cells. Occasional eos, neuts
PAS stain highlight Mott cells- Russel bodies are rich in carbohydrates
50% cats are FIV +!!!
Elevated globulins on Chem. Possible concurrent plasma cell stomatitis, immune-mediated glomerulonephritis, renal amyloidosis.
English bulldog. Dorsal neck.
Calcinosis cutis
Deeply basophilic mineral throughout the superficial/mid-dermis. Granulomatous inflammation. Transepidermal elimination of mineral.
HAC
Bone in late stages = osteoma cutis
Dog, cat. Scaly, alopecia
Dermatophytosis
Multifocal pyogranulomatous folliculitis and furunculosis with dermatophytic hyphae +/- arthrospores. May see pustular variant with acantholytic keratinocytes (Trichophyton)
Dog
Demodicosis
Pyogranulomatous mural folliculitis and furunculosis with pigmentary incontinence and intrafollicular mites
Dog. Dorsum.
Post grooming furunculosis
Pyogranulomatous furunculosis with hemorrhage and edema. Hemorrhagic bullae with fibrin within dermis
PAINFUL. Pseudomonas aeruginosa usually. Bath 1-2d before presentation
Dog
Alopecia areata
Swarm of bees around anagen hair follicle = lymphoplasmacyticbulbitis.
+/- perifollicular fibrosis.
Associated with autoantibodies and complement around hair follicles. IgM, IgG to hair follicle antigens in circulation.
(Pseudopelade affects isthmus, bulge area)
Dog
Canine Cushing’s disease
Epidermal atrophy. Thin walled comedones. Follicular atrophy. +/- sebaceous gland atrophy.
Boston Terrier, Boxer, Dachshund, Mini poodle endogenous HAC. English bulldog iatrogenic HAC.
Pomeranian
Alopecia X
Epidermal atrophy w/ orthokeratotic hyperkeratosis in loose pattern. Telogenization of hair follicles w/flame figures and prominent tricholemmal keratin
Possible etiology: Late-onset deficiency of 21-hydroxylase leading to progestin and androgen excess at puberty
Cat. Systemically unwell. NOT FRAGILE skin, but wrinkled and thin
Feline paraneoplastic alopecia
Miniaturization of follicles (telogenization) and follicular atrophy. Acanthosis. Partial loss of stratum corneum
Shiny skin, painful pawpads. NOT FRAGILE skin, but wrinkled and thin
Pancreatic carcinoma
Malassezia pachydermatis infections!!
Bulldog
Hyperpigmented epidermis. Follicular keratosis. Atrophy of the lower portion of the hair follicle = “inverted witch’s foot”.
Boxers, bulldogs. Spring time.
Dog
Black Hair follicular dysplasia
Melanin clumping in hair shafts with breakage at the sites of clumping. Pigmentary incontinence around anagen hair bulbs.
Mini poodle
Post-rabies vaccination panniculitis
1) Follicular ischemic atrophy
2) Multifocal lymphoid nodules in panniculus
3) Amphophilic adjuvant substrate in subcutis
Poodles over-represented. “Poodle patch”. Right rear thigh, but can have lesions away from vaccine spot.
Pug
Pigmented viral plaque
Orderly maturation of keratinocytes
D/E junction has scalloped appearance. Hyperpigmentation, enlarged keratohyalin granules. No viral inclusions
CPV-9 CPV-4, CPV-8
Pugs, Mini schnauzers, Boston Terrier, Frenchies.
Can progress to trichoepithlioma or SCC
Horse
Squamous cell carcinoma
Infiltrative beyond the BMZ, unencapsulated lobules of epithelial cells with multifocal keratin pearls. Anisocytosis, Anisokaryosis. Mitotic activity HIGHER than IKA.
+/- Solar elastosis.
UV light. Cancer eye in Hereford cattle. Paint horses. Non-pigmented skin in cats (nasal planum, pinnae, eyelids)
10 yo cat
Bowenoid in situ carcinoma
RESPECTS BMZ
Hyperplastic and dysplastic epithelial without breaking through BMZ. No viral inclusions
Associated with FcPV-2
Dog
Canine Ribbon-Type Trichoblastoma
Basal cell tumor
Cat
Feline Trabecular-type Trichoblastoma
Basal cell tumor
Often pigmented in cats
Older cat front paw
Metastatic Pulmonary Carcinoma
Multifocal tubules lined by ciliated respiratory epithelium w/goblet cells. May infiltrate ST and bone.
Chest rads: Single, large circumscribed mass in CAUDAL LEFT lung field.
Paw Radiograph: osteolysis of digit.
Horse
Equine sarcoid
Epidermal rete ridge formation that extends into deep dermis. “Picket fence” pattern: perpendicular fibroblasts relative to BMZ
BPV 1, BPV2. Major transforming viral protein = E5
E5 downregulates MHC 1 –> evade immune destruction by CD8 T cells
Old dog
Cutaneous epitheliotropic lymphoma
Neoplastic lymphocytes w/tropism for epithelium, esp follicular epithelium and apocrine sweat glands. Usually lower 1/2 epidermis. Pautrier’s microabscesses.
IHC= CD3+ T cells
PARR for clonality
