Primary malignant hemangiopericytoma of the breast: report of a case.

A 70-year-old woman presented with a huge tumor in her left breast, which had rapidly increased in size causing cutaneous erosion. She underwent a simple mastectomy, at which time the tumor was found to be an encapsulated multilocular cystic lesion containing dark fluid. Histological examination disclosed the characteristic features of malignant hemangiopericytoma, including the perivascular lamellar growth of atypical mesenchymal cells with vimentin-positive cytoplasm. Multiple irregular vascular luminal formation was also conspicuous. The characteristics of this lesion are discussed together with a review of the previous literature on this unusual neoplasm.