Extraskeletal osteosarcoma located to the gallbladder.

Extraskeletal osteosarcoma is a rare malignant soft tissue tumour. At open cholecystectomy performed for gallstones, a 61-year-old woman was found to have osseous tissue in the wall of the gallbladder. Histopathological examination of the specimen revealed a focus of extraskeletal osteosarcoma. The patient developed widespread intra-abdominal metastases 5 months after the operation, and died of pulmonary deposits at 9 months. Although osteosarcoma has rarely been reported at other extraskeletal sites, this appears to be the first case of a primary tumour in the gallbladder.