Radiation-associated extraskeletal osteosarcoma of the chest wall.

Radiation-associated sarcoma is a rare but potential complication of radiation therapy. Most reported cases of osteosarcoma of the chest wall following radiation therapy for breast cancer arise from the chest wall skeletal structures. In contrast, few cases of extraskeletal osteosarcomas have been reported. We report a rare example of an extraskeletal osteosarcoma involving the pectoralis major muscle occurring after radiation therapy for breast cancer. Extraskeletal osteosarcomas are rare soft tissue tumors with a high rate of local recurrence and a poor prognosis.