Malignant Fibrous Histiocytoma with Epithelial Differentiation?

A case of recurrent soft part sarcoma with focal areas showing epithelial differentiation in the right thigh in a 78-year-old woman is reported. The primary tumor consisted of myxoid areas and solid areas, in which relatively uniform epithelioid tumor cells were arranged in sheets, whereas pleomor-phism and a storiform pattern appeared in the recurrent tumors. Thus this tumor was suspected to be a malignant fibrous histiocytoma. However, further studies showed unexpected ultrastructural and immunohistochemical features. Cytokeratin immu-noreactivity and tonofilamentlike structures probably indicated epithelial differentiation of some tumor cells. From the clinical and histological findings, this tumor should be identified as a malignant fibrous histiocytoma with phenotypic expressions of epithelial cell.