What Is It?
Osteosarcoma is the uncontrolled growth of abnormal cells in bone. Although it is the most common type of bone cancer, it is rare.
Osteosarcoma typically appears as a mass of abnormal bone in an arm or leg, usually near the knee or shoulder. Less often, the tumor develops in the pelvic bones, jaw, or ribs. It rarely develops in the fingers or toes. At the time of diagnosis, 10% to 20% of osteosarcomas have spread (metastasized) to another part of the body, usually the lungs.