Postirradiation epithelioid angiosarcoma of the breast: a case report with immunohistochemical and electron microscopic study.

A case of postirradiation epithelioid angiosarcoma of the breast in a 72-year-old woman is reported. She had had right breast conserving surgery, axillary lymph node dissection, and 50 Gy external beam radiation therapy for infiltrating ductal carcinoma. A skin lesion on the irradiated breast appeared 5 years after completion of radiation. Angiosarcoma was diagnosed in a contralateral axillary mass 8 months later. Light microscopically, the tumor was characterized by a sheet-like growth of epithelioid cells with focal vasoformative areas. Tumor cells were reactive for factor VIII-related antigen, cytokeratin and CD34. Electron microscopically, the tumor cells were round with smooth cell borders. They were closely apposed, occasionally forming a small lumen containing single red blood cells or aggregates of platelets. Groups of tumor cells were enclosed by an external lamina. The tumor cells had abundant cytoplasm with sparse organelles. Rare suggestive Weibel-Palade bodies were present. The immunohistochemical and ultrastructural findings in this postirradiation tumor were in agreement with previously reported findings in non-irradiation-induced epithelioid angiosarcomas.