The punch biopsy specimen demonstrated an increased number of capillaries and venules in the upper dermis, associated with a few inflammatory cells, some of which were multinucleate with a focal angulated shape. The epidermis appeared normal. Immunohistochemical studies revealed that the multinucleate cells were positive for vimentin and negative for CD34, CD68, S100 protein, and factor VIII–related antigen. The vessels expressed CD34 and factor VIII–related antigen.
Multinucleate cell angiohistiocytoma is a benign vascular tumor that predominantly affects the acral sites of elderly women and may clinically mimic the patch and plaque stage of Kaposi sarcoma. It was first described by Smith and Wilson-Jones1 in 1985, and since then, only 42 additional cases have been reported in the literature.2 It is characterized by the proliferation of dermal capillaries and venules, and occasionally small arterioles, mixed with diffuse or discrete foci of lymphocytes and histiocytes.The most striking histologic finding is the presence of several large multinucleate giant cells, although the density of the giant cells is usually relatively sparse.3
Asymptomatic, Smooth, Violaceous Papules of the Thighs—Diagnosis. Arch Dermatol. 2003;139(7):933-938. doi:10.1001/archderm.139.7.933-a