The most common malignant tumor of bone. It arises from osteoblastic cells. Patients typically present with bone pain or a mass. The long bones are most commonly affected, and the tumor frequently metastasizes to other locations, especially the lung. Osteosarcoma is most common in males under 30 years of age. It can also occur secondary to medical conditions such as Paget disease and prior radiotherapy. Osteosarcoma is treated with chemotherapy and surgical excision of the primary tumor. With treatment, overall survival is approximately 60%-80%.