Epithelioid cell histiocytoma: a report of 10 cases including a new cellular variant

Epithelioid cell histiocytoma is a recently recognized lesion that is considered to be a variant of cutaneous fibrous histiocytoma (dermatofibroma). Ten cases are presented, including their light microscopic, immunohistochemical, and ultrastructural features. Eight of the cases are similar to those previously reported, presenting as elevated nodules arising on the extremities and composed of epithelioid histiocytes with overlying epidermal effacement. Two of the cases were composed of cells with the same morphologic and immunohistochemical characteristics as typical epithelioid cell histiocytoma, including factor XIIIa positivity, but these arose in the reticular dermis and exhibited prominent cellularity.