ABD Dermatopathology flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Spongiotic dermatitis

Microscopic pattern with intercellular edema in the epidermis; eosinophils favor allergic contact or drug reaction, while neutrophils in the stratum corneum suggest impetiginization.

Lichen planus histology

Interface dermatitis with wedge-shaped hyperkeratosis, saw-tooth rete ridges, and a bandlike lymphocytic infiltrate obscuring the dermoepidermal junction; PAS highlights basement membrane thickening.

Pemphigus vulgaris DIF

Direct immunofluorescence shows intercellular IgG and C3 in the epidermis, producing a chicken-wire pattern; serum antibodies target desmoglein 3.

Bullous pemphigoid DIF

Direct immunofluorescence reveals linear IgG and C3 along the basement membrane zone; salt-split skin shows epidermal roof staining, distinguishing it from epidermolysis bullosa acquisita.

Dermatitis herpetiformis DIF

Direct immunofluorescence shows granular IgA deposits in dermal papillae; associated with gluten-sensitive enteropathy and celiac disease.

Leukocytoclastic vasculitis

Small-vessel vasculitis with fibrinoid necrosis, neutrophilic dust, and extravasated red cells; direct immunofluorescence may show granular IgA in Henoch-Schonlein purpura.

Sarcoidal granuloma

Naked noncaseating granulomas with sparse lymphocytic rim in the dermis; seen in sarcoidosis, and Schaumann bodies or asteroid bodies may be present.

Breslow thickness

Measured in millimeters from the granular layer of the epidermis to the deepest invasive melanoma cell; used for staging and sentinel node decisions.

Benign nevus maturation

Nevus cells become smaller and less nested with increasing dermal depth; lack of maturation and deep mitoses favor melanoma.

Pagetoid scatter

Atypical melanocytes spread upward through the epidermis, a feature of melanoma; it can also occur in Spitz nevi and sun-damaged skin.

HMB-45 expression

Immunostain marks melanocytic cells and typically diminishes with dermal depth in benign nevi; retained deep expression or PRAME positivity favors melanoma.

Lentigo maligna

Melanoma in situ on sun-damaged skin with atypical melanocytes along the dermoepidermal junction; it may progress to invasive lentigo maligna melanoma.

Spitz nevus

Benign melanocytic lesion with spindle or epithelioid cells, Kamino bodies, and maturation; atypical Spitz tumors require molecular testing for risk assessment.

Sentinel lymph node biopsy

Identifies early nodal melanoma metastasis using immunohistochemistry for S100, SOX10, and Melan-A; positivity affects staging and treatment.

Actinic keratosis

Atypical keratinocytes confined to the lower epidermis over sun-damaged skin; full-thickness atypia indicates squamous cell carcinoma in situ.

Basal cell carcinoma

Nests of basaloid cells with peripheral palisading, clefting, and mucin; Ber-EP4 immunostain is positive, helping distinguish it from squamous cell carcinoma.

Keratoacanthoma

Crateriform squamous proliferation with a central keratin plug and glassy cytoplasm; it may regress spontaneously but can show invasive features.

Pilomatricoma

Adnexal tumor with basaloid cells and ghost cells, often with calcification; it typically presents as a firm nodule in children.

Sebaceous adenoma

Benign sebaceous neoplasm with lobules of sebocytes and mature sebaceous cells; multiple lesions may indicate Muir-Torre syndrome.

Merkel cell carcinoma

Neuroendocrine carcinoma with small blue cells, dotlike CK20, and CM2B4 positivity; it is aggressive and often associated with Merkel cell polyomavirus.

Mycosis fungoides

Cutaneous T-cell lymphoma with epidermotropic atypical lymphocytes, Pautrier microabscesses, and a CD4-positive T-cell phenotype with loss of CD7.

Pautrier microabscess

Intraepidermal cluster of atypical lymphocytes seen in mycosis fungoides; it is a helpful but not entirely specific diagnostic clue.

Langerhans cell histiocytosis

Proliferation of Langerhans cells with grooved nuclei, eosinophils, and positivity for S100, CD1a, and langerin; it can affect skin, bone, and other organs.

Mastocytosis

Dermal infiltrate of mast cells with tryptase and CD117 positivity; CD25 expression and urticaria pigmentosa are common, and systemic disease needs staging.

Leukemia cutis

Leukemic infiltrate in skin, often with a Grenz zone and perivascular or periadnexal distribution; immunohistochemistry helps classify myeloid or lymphoid lineage.

Rosai-Dorfman disease

Histiocytic proliferation with emperipolesis, S100 positivity, and CD1a negativity; it often presents with massive lymphadenopathy but can involve skin.

Dermatofibroma

Benign fibrous histiocytoma with collagen trapping, epidermal hyperplasia, factor XIIIa positivity, and CD34 negativity; it typically feels firm on palpation.

Dermatofibrosarcoma protuberans

Storiform spindle cell tumor with CD34 positivity and COL1A1-PDGFB fusion; it is locally aggressive and requires wide excision.

Kaposi sarcoma

Vascular tumor with slit-like spaces, spindle cells, and HHV8 positivity; it is associated with immunosuppression and presents as violaceous plaques or nodules.

Infantile hemangioma

Benign vascular tumor with GLUT1 positivity, distinguishing it from vascular malformations; it typically grows after birth and then involutes.

Schwannoma

Peripheral nerve sheath tumor with Antoni A and B areas, Verocay bodies, and S100 positivity; it is usually encapsulated and benign.

Direct immunofluorescence

Technique using labeled antibodies to detect immune deposits in skin; patterns help diagnose pemphigus, pemphigoid, dermatitis herpetiformis, and lupus.