ANGIOSARCOMA ARISING IN A SOLITARY SCHWANNOMA (NEURILEMOMA) OF THE SCIATIC-NERVE

Angiosarcomas rarely develop within a peripheral nerve or a peripheral nerve sheath tumor. We describe an epithelioid angiosarcoma that aros e in a benign schwannoma (neurilemoma) of the right thigh in a 65-year -old man who did not have von Recklinghausen's disease. Histologically , the resected tumor was a high-grade undifferentiated sarcoma that wa s predominantly arranged in solid sheets or nests and composed of epit helioid cells. The endothelial origin of the tumor was suggested by Fa ctor VIII R-ag, Ulex europaeus-I, CD34, CD31, BNH9, and vimentin immun oreactivity, along with the ultrastructural evidence of occasional Wei bel-Palade bodies. In this location, epithelioid angiosarcoma should b e distinguished from malignant transformation of a schwannoma with epi thelioid changes. This observation stresses the importance of immunohi stochemical and ultrastructural analysis in the differential diagnosis of vascular tumors with features of epithelioid sarcoma.