Müllerian carcinosarcomas occurring outside the female genital tract are extremely rare but occasionally they may arise from the peritoneum as part of the secondary müllerian system. This report describes two cases of extragenital müllerian carcinosarcoma with heterologous elements in the form of malignant cartilage. We wish to highlight the fact that these aggressive neoplasms may occasionally have a peritoneal origin, similar to primary peritoneal serous carcinomas.