Multinucleate-cell angiohistiocytoma occurring in a patient with mycosis fungoides.

Multinucleate-cell angiohistiocytoma (MCAH) is a benign vascular proliferation of unknown etiology. Clinically, MCAH presents as grouped, erythematous, or violaceous papules on the extremities in older women. These lesions often resemble Kaposi's sarcoma. Histologic examination reveals characteristic bizarre-shaped, multinucleate giant cells, some of which contain three to six nuclei arranged in a ring-like or overlapping pattern, which stain positively for Factor XIIIa. In addition, there is a proliferation of dermal capillaries and venules with a mild lymphohistiocytic infiltrate. To our knowledge, this is the first reported case of MCAH occurring in a patient with mycosis fungoides.