Leiomyosarcoma of the female breast: report of two new cases and a review of the literature.

We present the clinical, light microscopic, and immunohistochemical features of two new cases of leiomyosarcoma of the female breast. Both the patients were old (83 and 86 years) and were referred with a history of a long-standing breast lump. The results of the physical examination and the preoperative radiologic investigations suggested a phyllodes tumor. The patients were treated with mastectomy. The tumors measured 6 and 6.5 cm in the largest dimension, respectively, and were composed of fascicles of atypical, actively proliferating spindle cells, often intersecting at right angles. The axillary lymph nodes were free of tumor. Immunohistochemically, the tumor cells were positive for desmin, muscle-specific actin, and vimentin and negative for other markers, including keratins and hormone receptors. Focal rhabdomyoblastic differentiation was noted in one case. Follow up at 1 year is negative for metastases or local recurrences. Our study confirms that leiomyosarcoma of the breast is a locally invasive neoplasm and that it could represent a peculiar anatomic entity among mesenchymal tumors of the breast.