Skin Flashcards
Skin with perivascular inflammation comprised predominantly of neutrophils, with cellular debris, extravasation of red blood cells, vessel wall expansion and fibrinoid necrosis.
Leukocytoclastic vasculitis
Differential diagnosis:
Specific forms of leukocytoclastic vasculitis:
IgA vasculitis (Henoch-Schonlein purpura)
IgM/IgG vasculitis
Cryoglobulinaemia
Plan:
Correlate with clinical history and dermatologic impression (?drug/allergy/infection exposure ?renal/GI manifestations ?Hepatitis/HIV)
Correlate with any concurrent pathology testing (e.g. serum cryoglobulins)
Correlate with direct immunofluorescence findings (?specific pattern of staining)
Advice to clinician: Leukocytoclastic vasculitis is a general pattern of cutaneous small vasculitis and has multiple potential causes. Clinical correlation is required.
Nodular dermal proliferation of highly pleomorphic spindle cells. May have melanoma in situ in overlying skin.
Spindle cell melanoma
Differential diagnosis:
Spindle cell SCC
Leiomyosarcoma
Angiosarcoma, Atypical fibroxanthoma (AFX)
Plan:
Correlate with clinical history and dermatologic impression
IPX to support Dx: S100 SOX10 and Melan A.
IPX to discount DDx: AE1/AE3 and CAM5.2, SMA and desmin, CD34, CD10 and CD68
Next steps: Synoptic report, discuss at MDT
Poorly circumscribed dermal lesion with elongated spindle cells in abundant collagen, with scattered hyperchromasia/pleomorphism and lymphoid aggregates. May have melanoma in situ in overlying skin.
Desmoplastic melanoma
Differential diagnosis:
Dermal scar
Plan:
Correlate with clinical history and dermatologic impression (?history of previous biopsy/procedure)
IPX to support Dx: S100 and SOX10.
Next steps: Synoptic report, discuss at MDT
Skin with nests of atypical melanocytes along dermoepidermal junction with pagetoid spread, without extension into dermis
Melanoma in situ
Differential diagnosis:
Extramammary Paget’s disease
Squamous cell carcinoma in situ
Plan:
Correlate with clinical history and dermatologic impression
IPX to support Dx: S100 SOX10 and Melan A.
IPX to discount DDx: CK5/6, CK7
Next steps: Synoptic report, discuss at MDT
Skin with confluent nests of atypical melanocytes along dermoepidermal junction with pagetoid spread, and extending into dermis centrally without maturation and with dermal mitoses.
Superficial spreading melanoma
Plan:
Correlate with clinical history and dermatologic impression
IPX to support Dx: S100, SOX10, and Melan A.
Next steps: Synoptic report, discuss at MDT
Polypoid/exophytic skin tumour with nests and sheets of atypical dermal melanocytes, with minimal junctional component, and no intraepidermal spread lateral to tumour
Nodular melanoma
Plan:
Correlate with clinical history and dermatologic impression
IPX to support Dx: S100, SOX10, and Melan A
Next steps: Synoptic report, discuss at MDT
Nests of basaloid cells with frequent mitoses which undergo abrupt transition into ‘ghost’/’shadow’ cells. Associated calcification and foreign body giant cell reaction to keratin.
Pilomatrixoma
Plan:
Correlate with clinical history and dermatologic impression
No specific action required for this benign diagnosis
Skin with dense band-like lymphocytic infiltrate, and with interface dermatitis (Civatte bodies in the basal layer and sometimes higher epidermis). The epidermis is also hyperkeratotic with prominent granular layer and irregular sawtooth acanthosis.
Lichen planus
Differential diagnosis:
Lichenoid keratosis (if solitary lesion)
Lichenoid or fixed drug eruption
Plan:
Correlate with clinical history and dermatologic impression
Special stains: PAS (highlight Civatte bodies)
Skin/micosa with ill defined proliferation of bland, round to ovoid cells with eosinophilic granular cytoplasm. Overlying skin/mucosa may show pseudoepitheliomatous hyperplasia.
Granular cell tumour
Plan:
Correlate with clinical history
Examine further sections (e.g. for size, relation to margins)
IPX to support Dx: S100, CD68
No specific further action required for this benign diagnosis.
Dermal tumour with nodules, sheets, nests, and trabeculae of small round blue cells with finely dispersed chromatin, nuclear moulding, and frequent mitoses, apoptoses, and crush artefact
Merkel cell carcinoma
Differential diagnosis:
Metastatic small cell neuroendocrine carcinoma
Plan:
Correlate with clinical history and radiology (?known neuroendocrine tumour in another site)
Examine further blocks (e.g. for total size, relation to margins)
IPX to support Dx: Synaptophysin, chromogranin, CK20 (expect perinuclear ‘dot-like’ positivity
IPX to discount DDx: TTF1, CDX2
Next steps: Synoptic report, discuss at MDT
Well circumscribed dermal tumor composed of haphazardly arranged highly atypical spindle cells with abundant eosinophilic cytoplasm and occasional multinucleated cells
Atypical fibroxanthoma (AFX)
Differential diagnosis:
Pleomorphic dermal sarcoma (if bigger, deeper, with adverse features)
Spindle cell SCC
Leiomyosarcoma
Angiosarcoma
Spindle cell melanoma
Plan:
Correlate with clinical history and dermatologic impression
Examine further sections (e.g. for total size, relation to margins, any in-situ lesion in epidermis)
IPX to support Dx: CD10, CD68
IPX to discount DDx: AE1/AE3, SMA and desmin, CD34, S100 and SOX10
Next steps: Synoptic report
Sharply demarcated epidermal lesion composed of bland basaloid keratinocytes with hyperpigmentation and keratin horn pseudocysts
Seborrhoeic keratosis
Plan:
Correlate with clinical history and dermatologic impression
No specific further action required for this benign diagnosis
Pseudoepitheliomatous hyperplasia of the epidermis with suppurative dermal granulomatous inflammation containing septate, thick walled copper-coloured fungi (Medlar / muriform / sclerotic bodies).
Chromoblastomycosis
Plan:
Correlate with clinical history (?travel to endemic area ?slowly progressive lesion on extremity)
Correlate with concurrent microbiology investigations (culture) - if available, send fresh tissue for fungal culture
Special stains: Gram, PAS, GMS, ZN/modified ZN
Advice to clinician: A chronic fungal infection which is rare in Australia and most common in the tropics. Caused by multiple fungi found in wood, soil, and decaying plant material
Well demarcated dermal proliferation of bland spindle cells in storiform architecture or short curly fascicles, with collagen trapping at periphery, overlying Grenz zone and epidermal hyperplasia / hyperpigmentation. Spindle cells have thin, elongated nuclei with pointed ends and eosinophilic cytoplasm
Dermatofibroma
Differential diagnosis:
Dermal scar
Blue naevus (if pigmented)
DFSP (if cellular)
Plan:
Correlate with clinical history and dermatologic impression
IPX to support Dx: Factor XIIIa
IPX to discount DDx: S100, CD34 (would be diffuse in DFSP, stain periphery only in DF)
No specific further action required for this benign diagnosis.
Storiform architecture or short curly fascicles of monomorphic spindle cells in dermis with extensive subcutaneous involvement along fibrous septa (honeycomb pattern). No overlying epidermal hyperplasia.
Dermatofibrosarcoma protuberans
Differential diagnosis:
Cellular dermatofibroma
Nodular fasciitis
Solitary fibrous tumour
Plan:
Correlate with clinical history and radiology
Examine further sections (e.g. for size, relation to margins, fibrosarcomatous transformation)
IPX to support Dx: CD34 (expect diffuse positivity)
IPX to discount DDx: Factor XIIIa, STAT6
Next steps: Synoptic report, discuss at MDT
Nodular endophytic squamous tumour with central keratin filled crater, and prominent underlying inflammatory infiltrate. Cells have glassy eosinophilic cytoplasm.
Keratoacanthoma
Plan:
Correlate with clinical history and dermatologic impression
IPX to support Dx: Not required
Advice to clinician: Some pathologists regard this as a seperate entity, while others regard it as a variant of well differentiated squamous cell carcinoma. They have a characteristic clinical appearance and natural history of spontaneous regression.
Skin lesion with large nests of (possibly atypical looking) melanocytes in dermoepidermal junction and dermis, maturing with depth and breaking up into single melanocytes at base. DEJ shows eosinophilic hyaline globules (Kamino bodies) and clefting artefact from melanocyte nests
Spitz naevus
Plan:
Correlate with clinical history and dermatologic impression
Examine further sections (e.g. for total size, relation to margins, areas of atypical features)
IPX to support Dx: S100, HMB45 (expect HMB45 to show maturation, with decreased staining in the deeper parts of the lesion)
No specific further action required for this benign diagnosis.
Uniform acanthosis (epidermal hyperplasia with elongation of rete ridges), with ‘suprapapillary thinning’ (thinning of epidermis over dermal papillae), associated with parakeratosis, and collections of neutrophils (Munro’s microabscesses) within parakeratin layer. Dermis shows mild perivascular and interstitial infiltrate composed predominantly of lymphocytes, and dilated/tortuous capillaries within the dermal papillae.
Psoriasis
Differential diagnosis:
Fungal infection
Psoriasiform drug reaction
Lichen simplex chronicus
Subacute spongiotic dermatitis (e.g. eczema, allergic contact dermatitis, nummular dermatitis)
Plan:
Correlate with clinical history and dermatologic impression (?distribution and evolution of lesions ?drug/infectious/irritant exposures ?chronic scratching)
Examine deeper levels
Special stains: PAS and GMS (for any fungal elements)
Skin with mild perivascular lymphocytic inflammation in dermis and and lymphohistiocytic inflammation along septa of subcutaneous fat. Early lesions may show ‘Miescher radial granuloma’ (A cluster of small histiocytes radially arranged around a central cleft). Older lesions show widening of septa with fibrosis and multinucleated giant cells.
Erythema nodosum
Plan:
Correlate with clinical history (?tender erythematous plaque in pre-tibial area ?infectious/drug exposure ?systemic disease)
Advice to clinician: Usually self limiting, may be idiopathic or due to a wide range of antecedent causes.
Skin with acute/chronic inflammatory changes and naked hair shafts
Pilonidal sinus
Plan:
Correlate with clinical history (?chronic abscess/sinus formation in gluteal cleft)
No specific action required for this benign diagnosis.
Skin with haphazardly arranged, thick hyalinized collagen bundles within the dermis, surrounded by bland fibroblasts
Keloid scar
Plan:
Correlate with clinical history and dermatologic impression (?history of biopsy/procedure)
No specific further action required for this benign diagnosis.
Skin tumour formed of small nests of basaloid cells with irregular shapes that fit together in a puzzle pattern, each surrounded by thick pink basement membrane material which can also form droplets within nests.
Cylindroma
Differential diagnosis:
Spiradenoma (‘blue balls’)
Plan:
Correlate with clinical history and dermatologic impression (?head/neck location ?Brooke-Speigler syndrome)
IPX to support Dx: Not required
Advice to clinician: May be sporadic, or assiociated with Brooke-Speigler syndrome, where multiple lesions occur. Clinical correlation is required.
Well circumscribed nodule in dermis with bland ducts, tubules, and islands of epithelial /myoepithelial cells set within a chondromyxoid stroma.
Chondroid syringoma (cutaneous mixed tumour)
Plan:
Correlate with clinical history and dermatologic impression (?head/neck location)
IPX to support Dx: Not required
No specific action required for this benign diagnosis.
Dermal cyst lined by stratified squamous epithelium, with granular layer, containing lamellated (‘flaky’) keratinous material in the cyst lumen.
Epidermal inclusion cyst
Plan:
Correlate with clinical history and dermatologic impression
No specific action required for this benign diagnosis
Dermal proliferation of bland, spindle shaped melanocytes admixed with melanophages in a dense collagenous background
Blue nevus
Differential diagnosis:
Dermatofibroma (pigmented)
Plan:
Correlate with clinical history and dermatologic impression
IPX to support Dx: S100, SOX10, and Melan-A.
IPX to discount DDx: Factor XIIIa
No specific further action required for this benign diagnosis
Skin with poorly circumscribed masses of macrophages (which may be foamy) in the dermis, with few / no lymphocytes, and predilection for nerves, vessels, and skin adnexa.
Lepromatous leprosy
Plan:
Correlate with clinical history and dermatologic impression (?travel or migration from endemic area)
Correlate with concurrent microbiology investigations (e.g. PCR). If not performed, parrafin block can be used for PCR.
Special stains to support Dx: Modified ZN (Wade-Fite) stain
Advice to clinician (urgent via phone): This is a rare disease in Australia and patient may require urgent treatment. Patient may also require infectious diseases precautions (public health implications)
Band like infiltrate of lymphocytes beneath epidermis, with prominent intraepidermal lymphocytes out of proportion to degree of spongiosis (epidermotropism). Lymphocytes are hyperchromatic with nuclear contour irregularity (cerebriform nuclei). May form small aggregates within epidermis (Pautrier microabscesses)
Mycosis fungoides
Differential diagnosis:
Inflammatory skin disease (e.g. psoriasis, atopic dermatitis, drug reaction, fungal/parasitic infection)
Sezary syndrome
Systemic T cell neoplasm (T cell leukaemia/lymphoma)
Plan
Correlate with clinical history and radiology
Examine deeper levels
Special stains: DPAS
IPX to support Dx: CD4, TCR-beta, CD2 (positive for CD4 and TCR-beta with loss of CD2 would support MF)
Next steps: Discuss at MDT
Nests and cords of bland melanocytes within dermis, with maturation towards the deep aspect. No melanocytes seen within dermoepidermal junction
Benign intradermal naevus
Plan:
Correlate with clinical history and dermatologic impression
Examine further blocks (e.g. for total size, relation to margins)
IPX to support Dx: S100, SOX10, MelanA, HMB45 (expect HMB-45 to show decreased staining deeper in lesion)
No specific further action required for this benign diagnosis
Sharply circumscribed vulval/perianal lesion with maze-like glandular and papillary architecture without connection to overlying epithelium. The glands are lined by an inner layer of cuboidal cells and an outer layer of myoepithelial cells. Mitotic figures are rare
Hidradenoma papilliferum
Plan:
Correlate with clinical history
Examine further blocks (e.g. for total size, relation to margins)
No specific further action required for this benign diagnosis
