Spindle cell hemangioendothelioma--a case report.

Spindle cell hemangioendothelioma is a rare vascular tumor which is presented with subcutaneous nodules and follows a benign indolent course but has a recurrent tendency, and is histologically resembling a cavernous hemangioma and Kaposi's sarcoma. We present a case of spindle cell hemangioendothelioma possessing clinical aggressiveness with painful bony erosion, histologic pleomorphism and mitoses. A 20-year-old man presented with a recurrent painful mass on the left ankle. The mass was dark brown and firm with irregular margins and measured 1.5 cm in diameter, which affected and eroded the underlying medial malleolus of the left tibia. Microscopically, the tumor was composed of cavernous endothelial-lined blood spaces and spindle cellular areas mimicking Kaposi's sarcoma. The spindle cells intermingled with plump epithelioid cells and showed a moderate degree of pleomorphism with occasional mitoses. Immunohistochemically, the spindle cells were focally positive for factor VIII-associated antigen and vimentin, and negative for S-100 protein, desmin, and epithelial membrane antigen.