Intracranial osteosarcoma after radiosurgery--case report.

A 56-year-old woman presented with an intracranial osteosarcoma at the site of previous radiosurgery, manifesting as sudden onset of headache and left hemiparesis with aphasia. She had a previous history of stereotactic radiosurgery for an intracranial tumor under a diagnosis of falx meningioma. Computed tomography showed intratumoral and peritumoral hemorrhage at the right parietofrontal region. Gross total resection of the tumor with hematoma was performed. The histological diagnosis was osteosarcoma. Sarcomatous change is a rare complication of radiotherapy. This case illustrates that osteosarcoma may develop years after radiosurgery for benign brain neoplasm.