Epithelioid angiosarcoma of the breast. Clinicopathological, immunohistochemical, and ultrastructural study of a case.

A breast tumor with features of epithelioid angiosarcoma (EAS) occurring in a 26-year-old woman is described. The lesion on lumpectomy was initially diagnosed as infiltrating ductal carcinoma and treated accordingly by radical mastectomy. The surgical specimen disclosed a high-grade tumor characterized by solid groups and sheets of atypical polygonal epithelioid cells displaying cytoplasmic microlumina alternating with anastomosing vascular channels. The endothelial nature of the epithelioid cells was demonstrated by the presence of vascular endothelium-associated markers by immunohistochemical and ultrastructural studies. The clinical features of this rare, hitherto undescribed lesion are similar to those of conventional breast angiosarcoma. The recognition of this entity is crucial because it can be confused with neoplasms displaying epithelial cytomorphology such as ductal carcinoma, pseudoangiosarcomatous carcinoma, metaplastic carcinoma, and epithelioid hemangioendothelioma. EAS should be added to the list of conditions that may present as a discrete tumor mass of the breast in young women.