1 Electrocautery Keratinocytes show marked parallel vertical elongation Homogenization of the collagen 2 Gelfoam Blue-purple, arabesque, netlike pattern with surrounding granulomatous reaction 3 Aluminum chloride Epidermal effacement and horizontal fibrosis consistent with scar and underlying light gray-blue granules, often in…
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…
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…
Pseudoxanthoma elasticum Key Features Curled and frayed, calcified elastic fibers in the reticular dermis (pink or blue squiggles) Elastic tissue (Verhoeff–Van Gieson) and calcium (Von Kossa) stains highlight the distorted elastic fibers Pseudoxanthoma elasticum is an autosomal-recessive and, less commonly,…
Granulomas are discrete collections of histiocytes with or without multinucleate giant cells. Histiocytes are bone marrow derived or mesenchymal. In granulomas, their cytoplasmic membranes touch with no intervening connective tissue. Infectious etiologies, especially fungal and mycobacterial, should be excluded with…
Glossary of terms Acantholysis Loss of cell–cell adhesion Acanthosis Increase in thickness of the epidermis Regular (all rete pegs descend to the same level) or irregular (rete pegs descend to different levels in the papillary dermis) Anaplasia Atypical nuclei (abnormal…