Pediculosis The Parasites, Pathogenesis, and Epidemiology Pediculosis is an infestation by one of several species of sucking lice of the phylum Arthropoda, class Insecta, order Phthiraptera, suborder Anoplura, and family Pediculidae or family Pthiridae. The three types of lice that…
Angiokeratoma Key Features Hyperkeratosis Acanthosis Ectatic, thin-walled vessels in contact with the epidermis Resembles a “bloody seborrheic keratosis” Lymphangioma Key Features “Frog spawn” clinically Similar to angiokeratoma with lymph in vessels, but few erythrocytes D2-40+ Nevus flammeus Key Features Dilated…
Dermatofibroma Key Features Interstitial spindle cell proliferation Collagen trapping Overlying platelike acanthosis Follicular induction common Ringed lipidized siderophages or perivascular collagen donuts may be present Factor XIIIa+ CD34− All dermatofibromas demonstrate a proliferation of fibrohistiocytic cells. A curlicue pattern is…
Viral infections Warts Verruca vulgaris Key Features Exophytic Papillomatosis Compact eosinophilic hyperkeratosis Coarse hypergranulosis in dells Vertical tiers of round parakeratosis common above peaks Blood and serum common above peaks Koilocytes variable The biopsy will demonstrate a compact stratum corneum,…
Tinea Key Feature Nonpigmented hyphae in stratum corneum The stratum corneum may be basket-weave or compact and eosinophilic. It may contain parakeratosis or clusters of neutrophils. Pearl The stratum corneum in tinea is commonly basket-weave, but a narrow zone of…
Bacterial diseases Impetigo Key Features Neutrophilic crust Chains or clusters of cocci Impetigo recruits neutrophils to the stratum corneum. Organisms are commonly visible in hematoxylin and eosin sections. Gram stain and culture may be required. Differential Diagnosis Collections of neutrophils…
The inflammatory infiltrate in septal panniculitis spills over into the lobule. The inflammation in lobular panniculitis often involves the septum; therefore septal and lobular panniculitis are best differentiated by the architecture of the lobule. In septal panniculitis, the lobule is…
Noninflammatory alopecia Transverse (horizontal) sections are generally best for evaluation of noninflammatory alopecia. Vertical sections may be used if serial ribbons of sections are cut from the block. A combination of vertical and transverse sections is always acceptable. Pattern alopecia…
Leukocytoclastic vasculitis (LCV) Key Features Perivascular infiltrate with neutrophils Karyorrhexis (nuclear dust, leukocytoclasis) Expansion of the vessel wall Fibrin deposition within the vessel wall Erythrocyte extravasation Clinical lesions of leukocytoclastic vasculitis are purpuric and often palpable. Vasculitis involving arterioles commonly…
Psoriasis Key Features Neutrophils above parakeratosis in stratum corneum Little to no serum in stratum corneum Alternating neutrophils and parakeratosis in the stratum corneum (sandwich sign) Neutrophilic spongiform pustules Little spongiosis in adjacent epidermis Tortuous blood vessels in dermal papillae…