Uterine tumor resembling an ovarian sex-cord tumor: report of a case of an endometrial stromal tumor with foam cells and ultrastructural evidence of epithelial differentiation.

Uterine tumors resembling ovarian sex-cord tumors are of uncertain histogenesis. We report such a neoplasm in which epithelial features observed by light microscopy were confirmed by electron microscopy and in which foam cells resembling those present in the stroma of hyperplastic endometria and in carcinoma represented a conspicuous intrinsic component. The lesion is interpreted as arising from endometrial stroma or multipotential uterine mesenchyme that has differentiated toward endometrial stroma and epithelium. The relationship of these uterine tumors to ovarian sex-cord stromal tumors and plexiform tumorlets is discussed.