Common type osteosarcoma is malignant. Common type osteosarcoma is malignant and refers to primary malignant bone or soft tissue tumors arising from osteoblastic mesenchymal cells, characterized by proliferating tumor cells that directly form bone or bone-like tissue. Osteosarcoma has a short course and rapid progression, and can show local jumping signs, and the tumor can even enlarge and expand significantly within a few days. In the early stage of the disease, there are no typical symptoms, only intermittent pain around the joints, which is aggravated by activities. In a few weeks, the pain may gradually increase and persist, and localized swelling may appear. Localized skin temperature increases and tenderness is evident. Severe patients may experience weight loss and anemia, and some may develop lung metastases. Treatment mainly includes surgery and radiotherapy. Therefore, common type osteosarcoma is malignant, and it should be treated actively after discovery to avoid deterioration.