Osteosarcoma is a cancer of the bone. It starts in immature bone cells that normally form new bone tissue destroys tissue, weakening the bone. Osteosarcoma can occur, very rarely, as a tumor of the soft tissues of the body, outside the bone itself. It usually occurs in adolescents and young adults, but can occasionally occur in younger children.
Osteosarcoma may be triggered by over-activity of bone cells and usually starts in the bones around the knee joint, in the upper or lower leg next to the knee, or in the thigh, but can begin in any bone in the body.
Most osteosarcomas develop in people who have no other diseases and no family history of bone cancer. In a very small number of families, siblings develop osteosarcoma. These families may be studied to see ifa rare genetic defect may be causing the tumor. If such a defect is found, it may help doctors identify other family members at risk and allow them to better understand the process by which cancer develops in other patients with osteosarcoma.
Researchers believe that osteosarcoma is may be caused by a combination of genetic changes that cause immature bone cells to become cancer cells instead of bone.