Histopathologic examination of the biopsy specimen revealed prominent capillaries in the mid to deep dermis with underlying collagenous stroma. Multinucleated giant cells with angulated and bizarre features were prominent within the fibrous stroma. The diagnosis of multinucleate cell angiohistiocytoma was made.
Multinucleate cell angiohistiocytoma (MCAH) is an uncommon, benign, vascular and fibrohistiocytic proliferation first described by Smith and Wilson Jones1 in 1985. Usually affecting women older than 40 years, MCAH manifests as single or multiple, reddish brown to violaceous, firm, dome-shaped papules, which may coalesce in an agminate pattern.2,3 Lesions are usually smaller than 1 cm and develop insidiously over several months or years. Multinucleate cell angiohistiocytoma is usually found on the lower extremities or dorsal aspect of the hands or wrists but has been reported on the forehead, cheeks, orbit, lower lid,upper lip, trunk, and oral cavity.2,3 The papules are typically asymptomatic but may be pruritic. The clinical differential includes Kaposi sarcoma, granuloma annulare, sarcoidosis, dermatofibroma, and, in this case, knuckle pads.
Skin-Colored Nodules on the Knuckles —Diagnosis. Arch Dermatol. 2011;147(8):975–980. doi:10.1001/archdermatol.2011.194-b
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