Multinucleate cell angiohistiocytoma: a clinicopathological, immunohistochemical and ultrastructural study.

The term 'multinucleate cell angiohistiocytoma' was first introduced by Smith and Wilson Jones in 1985. We report the clinicopathological, immunohistological and ultrastructural findings observed in two patients. Multinucleate cell angiohistiocytoma occurs mainly in middle-aged women and is usually located at acral sites, particularly the distal extremities. Grouped, brown-red, slightly elevated, asymptomatic papules slowly develop over several months until further growth ceases. There is no evidence of systemic disease. Histologically, the dermis shows numerous well developed capillaries with prominent endothelia, large bizarre basophilic and often multinucleate cells with a sparse lymphohistiocytic infiltrate. The immunohistological and ultrastructural findings suggest a fibroblastic differentiation of the large multinucleate cells.