Epithelioid angiosarcoma arising in a deep-seated plexiform schwannoma: a case report and literature review.

Angiosarcoma developing within a schwannoma is rare, and only 8 cases have been reported in the literature. Its association with a plexiform schwannoma has never been reported. We describe an epithelioid angiosarcoma arising in a plexiform schwannoma of the sciatic nerve in a 73-year-old man not known to have von Recklinghausen disease. Grossly, the tumor forms a long tubular mass with a multinodular growth pattern on the cut surface. Microscopically, these nodules display characteristics of a schwannoma, including Antoni A, Antoni B, and Verocay bodies. Adjacent to these nodules are high-grade anaplastic epithelioid cells growing in solid sheets, cords, and nests with focal vasoformative channels. The anaplastic cells are immunoreactive to CD31, CD34, and factor VIII related antigen, supporting their endothelial differentiation. Local recurrence and multiple pulmonary metastasis occurred 3 months after complete excision of the tumor. This case demonstrates the first occurrence of an epithelioid angiosarcoma in a deep-seated plexiform schwannoma with an aggressive clinical behavior.