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Epithelioid leiomyosarcoma of the breast: report of a case.

A 36-year-old female presented with a palpable mass in the right breast. She received a modified radical mastectomy after admission. Brain and multiple bony metastases were noted 10 months later. Microscopically, the tumor was composed of nodules of small spindle and large round cells showing abundant eosinophilic, vacuolated cytoplasm and prominent nucleoli. No glandular or ductular differentiation could be identified. By immunohistochemistry, the tumor cells were positive for vimentin and desmin in focal areas, but negative for cytokeratin, S-100, epithelial membrane antigen, actin, myoglobin, or alpha-1-antichymotrypsin. Electron microscopy showed focally cohesive large cells maintained together by poorly-defined intercellular junctions and surrounded segmentally by thin basal laminae. Intracytoplasmic filaments were identified in some tumor cells, diffusely arranged in the cytoplasm. These findings indicate that this was a case of epithelioid leiomyosarcoma of the breast. The literature concerning this rare neoplasm is reviewed.