Neurofibroma Key Features Loose arrangement with pale myxoid stroma Haphazard spindle cells with small wavy or S-shaped nuclei Mast cells are numerous Neurofibromas may occur as solitary lesions. Multiple widespread neurofibromas characterize neurofibromatosis (von Recklinghausen disease) in which they are…
Fat Lipoma Key Features Well-circumscribed tumor with a thin capsule Mature lipocytes Inconspicuous septae Lipomas typically present as asymptomatic, mobile, soft nodules in the deep soft tissue or subcutis. Histologically, they are thinly encapsulated tumors composed of sheets of mature…
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…
Mucinoses The mucinoses are a group of disorders characterized by mucin deposition in the dermis. The mucin is typically non–sulfated acid mucopolysaccharide (hyaluronic acid) that appears as wispy, faint blue threads on routine sections. It can be better appreciated with…
Lichen sclerosus (et atrophicus) Key Features Red (compact stratum corneum) White (papillary dermal pallor) Blue (lymphoid band beneath zone of pallor) Synonymous with balanitis xerotica obliterans on the glans penis Lichen sclerosus may involve skin or mucosa. Follicular plugging is…