Primary osteosarcoma of the uterus with peritoneal osteosarcomatosis: CT features.

A 67-year-old woman presented with lower abdominal pain for 1 month. Pelvic ultrasound revealed a calcified uterine mass and ascites. CT showed a heavily calcified uterine tumour, with ascites and disseminated calcified nodules in the peritoneum. Microscopic and immunohistochemical studies demonstrated features typical of osteosarcoma without any epithelial differentiation. Although rare, uterine osteosarcoma with associated peritoneal osteosarcomatosis should be included in the differential diagnosis of an elderly woman with a calcified uterine mass and disseminated peritoneal calcifications.