Introduction/Background Breast metaplastic carcinoma with mesenchymal differentiation, or carcinosarcoma, is a biphasic malignant tumor. It is composed of malignant epithelial and mesenchymal components. It accounts for less than 1% of all breast malignancies.Our aim was to discuss the clinical aspect, the anatomopathological characteristic, and the evolution of this rare entity.

Methodology We report nine cases of breast carcinosarcoma followed up at Salah Azaiez institute of oncology in Tunis between 2004 and 2022.

Results Our study enrolled nine female patients. The median age was 59 years. One patient had a medical history of breast carcinoma, treated 4 years before developing the carcinosarcoma. In six cases, the tumor was localized in the left breast and in the right side in three cases. Clinically, four patients had T2 tumors, one a T3, three a T4b, and one a T4d. The median size was 8 cm. In the histology, The tumor was triple negative in all cases. Eight patients had radical surgery.conservative surgery was performed in one case. The ninth patient had an adjuvant treatment with chemotherapy and radiation therapy. Metastatic recurrence to the lung and the liver was noted in two cases. The follow-up of the 7 other patients showed no signs of local or distant relapse.

Conclusion Breast carcinosarcomas are rare and aggressive entities. Their clinical and radiological aspects are non-specific. The treatment usually associates surgery to chemotherapy and radiation. Hormonal therapy has no place due to the usual absence of hormonal receptors.