CUTANEOUS EPITHELIOID CELL HISTIOCYTOMA - IMMUNOHISTOCHEMICAL AND ULTRASTRUCTURAL FINDINGS SUGGESTING ENDOTHELIAL ORIGIN

A 13-year-old boy presented with a polypoid nodule localized in the gr oin. Although the clinical and histopathological features corresponded to previously described diagnostic criteria of epithelioid cell histi ocytoma, immunohistochemical and ultrastructural findings suggested va scular differentiation of the epithelioid cells. In particular, the im munohistochemical negativity of the epithelioid cell elements for Fact or XIIIa failed to substantiate the previously forwarded hypothesis th at this lesion represents a dendrocytoma. Instead, the presence of his tiocytoid, vacuolated cells occasionally containing sparse red blood c ells, positive staining for Factor WI-related antigen, and ultrastruct ural evidence of endothelial characteristics in epithelioid neoplastic cells favor the hypothesis that ''epithelioid cell histiocytoma'' is of endothelial origin. We suggest the descriptive term cutaneous histi ocytoid hemangioendothelioma for this lesion.