What is bone cancer?

Primary bone cancer starts in the cells of your bones. Primary bone cancer is rare and is not the same disease as cancer that started somewhere else in the body and spread to the bones (called secondary bone cancer, or bone metastases).

Bones are made up of cells called osteocytes, osteoclasts and osteoblasts. These cells are held together by a hard, calcium-like material that makes the bone strong and rigid. The joints of the bones are covered in cartilage. Cartilage is a tough, flexible material that is more elastic than bone. It stops the bones from rubbing against each other and lets them move freely at the joints, like levers.

The skeleton provides a framework for our body and protects our vital organs. Bones are linked together by smooth cushions of cartilage at joints, like hips and knees. Although bones have different shapes, they are all made up of bone cells (osteocytes), nerves, blood vessels, connective tissue and minerals such as calcium. The bone marrow inside bones is where blood cells are made. The outer covering of a bone is called the periosteum.

The skeleton is made up of 206 bones of different shapes and sizes. The skeleton is the inner framework that supports your body. Bones also protect the organs inside the body. They store and release minerals (such as calcium and magnesium) that are important for your body. They also make and store blood cells in the marrow. Marrow is a soft, spongy material that fills most bones.

Throughout your life, bones constantly renew themselves by breaking down old bone cells and replacing them with new ones. If an abnormal cell develops, a tumour (benign or malignant) may start to grow in the bone. There are several types of bone cancer. Each type behaves differently and is treated differently.

Osteosarcoma is the most common type of bone cancer. It starts in new tissue in growing bones, most often in the knee area. Osteosarcomas tend to spread to other parts of the body, especially the lungs.
Chondrosarcoma begins in the cartilage. It usually grows slowly and rarely spreads to other parts of the body.
Ewing sarcoma begins in the cavity of the bone most often in the leg, arm or pelvis. It tends to grow quickly and spread to other parts of the body. (Ewing’s sarcoma can also start in the soft tissues rather than the bone. For information about Ewing sarcoma that starts outside the bone, call our Cancer Information Service at 1 888 939-3333)

Tumours that have spread to the bones from other cancers sites (secondary bone cancer or bone metastases) may be treated differently. For information about secondary bone cancer, please e-mail us or call our Cancer Information Service at 1 888 939-3333.

Last modified on: 13 December 2009