Uterine carcinosarcoma with melanocytic differentiation.

A 65-year-old black woman was found to have a 3.0 cm endometrial tumor that was a carcinosarcoma with a major epithelial and a less prominent mesenchymal component. The latter was undifferentiated but one focus of chondroid differentiation was noted. The former showed papillary serous differentiation. Melanin pigment was observed in both epithelial and mesenchymal components. Staining with antisera to S100 protein and HMB-45 confirmed the presence of melanocytes. An endocervical focus of tumor also contained melanin. Electron-microscopic studies showed large tumor cells with an irregularly indented nucleus and abnormal giant cytoplasmic melanosomes. Only one case of uterine carcinosarcoma with melanocytic differentiation has been previously reported.