We report a case of uterine corporeal heterologous carcinosarcoma suspected preoperatively of being small cell carcinoma. A 60-year-old woman admitted for abnormal genital bleeding was found in ultarasonography (US) to have an 8×8 cm uterine corporeal tumor and vaginal tumor. Vaginal tumor brushing cytology showed cells had a high N/C ratio and a granular chromatin pattern with ill-difined and crushed nuclei. Histologically, tumor cells proliferated in solid rosette formations and chondrosarcoma was also found. The woman was definitively diagnosed as having uterine corporeal heterologous carcinosarcoma.