Primary Osteosarcoma of Left Atrial Appendage in a Patient with Rheumatic Heart Disease.

Primary cardiac osteosarcoma is extremely rare, with all arising from the atrium, right ventricle, and cardiac valve, according to previous reports. We report a case of primary osteosarcoma of the left atrial appendage in a patient. We present a process of preoperative misdiagnosis, intraoperative confirmed diagnosis, and complete resection.