Ultrastructural and Immunohistochemical Study of Epithelioid Hemangioendothelioma of Bone: Coexpression of Epithelial and Endothelial Markers

Four cases of epithelioid hemangioendothelioma of bone—a borderline malignant tumor of vascular origin —were studied ultrastructurally and immuno histochemically. The epithelioid tumor cells were positive for vimentin, polyclonal and monoclonal cytokeratins, and the endothelial markers factor Vlll-related antigen (FVIII:RAg) and Ulex europaeus agglutinin I. The coexpression of polyclonal cyto keratin and FVIII:RAg was demonstrated by means of step sections in the same tumor cells. The endothelial origin of epithelioid tumor cells was supported ultrastructurally by identification of Weibel-Palade bodies.