Angiomatoid malignant fibrous histiocytoma. Report of two cases with ultrastructural observations of one case.

Two cases of so-called angiomatoid malignant fibrous histiocytoma are reported herein. One of the cases was studied ultrastructurally, representing, to my knowledge, the fourth such set of observations reported in the literature. It is concluded that the histiocytelike cells making up the bulk of the tumor are modified endothelial cells with histiocytic function, so that the term histiocytoid hemangioma may be a valid one. The principal point of difference, however, is that these tumors as described herein are aggressive with a potential both for local recurrence and metastasis.