Osteosarcoma is a type of primary bone cancer – one that starts in the bones, rather than spreads there from other sites. It is part of a group of cancers called sarcomas, that start in the connective tissues and bones. It begins in cells called osteoblasts that make the bone material.

The most common sites for osteosarcoma are the long bones, especially the thigh bone or femur close to the knee and the top of the upper arm bone (humerus) near to the shoulder although they can form in any bone. Osteosarcoma may initially cause pain or difficulty moving if it is near a joint, there may also be a lump or swelling. Very rarely the bone will fracture.

Treatment is surgery, usually limb-sparing surgery where the affected bone is removed and replaced with chemotherapy before and/or afterwards to reduce the size of the tumour and kill any remaining cells.