Osteosarcoma is a cancerous tumor that occurs in the bone. Osteosarcoma is a primary bone cancer. That means the cancer originates in the bone itself.

Most osteosarcomas appear in the long bones of the body, such as the femur (the thigh bone), the tibia (the shinbone) or the humerus (the bone that runs from the shoulder to the elbow), although they can appear in any bones.

Osteosarcoma is the oldest cancer known to man. A fossilized humanoid foot found in South Africa is 1.7m years old and it had osteosarcoma.