The occurrence of sarcoma in a benign cystic teratoma is very rare. We report the first poorly differentiated, malignant mixed mesodermal tumor with a component of rhabdomyosarcoma to arise in a benign cystic teratoma of the ovary. The tumor was staged as FIGO IC due to capsule invasion. Although combination chemotherapy of cisplatin, ifosfamide and mesna, was instituted, the disease took a rapidly progressive course. After an unusual metastasis to the scapula was detected, the patient deteriorated and died in the forth postoperative month.