Primary leiomyosarcoma in the breast.

The case is presented of a 62-year-old woman having a well-circumscribed, painless breast lump which led to the discovery of pure mammary leiomyosarcoma. There are only a few documented cases of primary leiomyosarcoma in the breast, and a brief review of the literature on the diagnostic findings and histogenesis of a smooth muscle malignant neoplasm in this site is, therefore, provided. As far as the histogenesis is concerned, ultrastructural features of the present case suggest a tumor of pluripotent mesenchymal cell nature rather than of vascular smooth muscle cell origin.