Uterine carcinosarcoma (malignant mixed Müllerian tumor, MMMT) is a rare aggressive malignant tumor, which demonstrates both malignant epithelial (carcinoma) and mesenchymal (sarcoma) components. Synchronous uterine carcinosarcoma and contralateral breast cancer in patient received tamoxifen treatment had not been reported. We present a case of uterine carcinosarcoma co-occurrenced with contralateral breast cancer in a 56-year-old nulliparous, obese breast cancer patient, who had been treated with tamoxifen for 5 years. The patient presented with palpable pelvic mass and vaginal bleeding. Histopathological evidence revealed that the tumor was comprised of an admixture of malignant epithelial and mesenchymal components. The epithelial component was endometrioid type adenocarcinoma, while sarcomatous component had heterologous elements including fusiform cell sarcoma and a prominent component of cartilage. The infiltrating ductal carcinoma has been diagnosed on her right breast. The patient died of disease 8 months after diagnosis. Postmenopausal patients, with adjuvant tamoxifen treatment for breast cancer, are at increased risk for the development of uterine carcinosarcoma and less benefit for contralateral breast cancer.
Keywords: Uterine carcinosarcoma; contralateral breast cancer; tamoxifen.