Osteosarcoma is a type of bone cancer in which malignant (cancerous) cells produce immature bone.
Osteosarcoma is rare. According to the American Cancer Society, some 800 cases of osteosarcoma are diagnosed annually in the nation. About half of these are in children and teens. This accounts for about 3% of pediatric cancers.
Nearly 80% of the tumors are in the thighbone (femur) or lower leg bones (tibia or fibula). They also may develop in the upper arm bone (humerus). Usually, tumors develop during “growth spurts,” or periods of rapid growth in the teen years.
Although osteosarcoma may appear to be in only one location in the lower leg or forearm, almost all patients have tumor cells called micrometastases in the lungs.
Bones support, give structure to body
Bones, which usually are hollow, have three main parts:
Matrix: The outer part of bones, which is made of fiber-like tissue and covered with a layer of tissue called the periosteum.
Bone marrow: The soft tissue in the space in hollow bones, which is called the medullary cavity. Cells inside bone marrow include:
- Fat cells
- Red blood cells, white blood cells and platelets
- Fibroblasts, a type of cell that helps build connective tissue
- Plasma, in which blood cells are suspended
Cartilage: Material that is at the end of most bones. It is softer than bone, but it is firmer than soft tissue. Cartilage and other tissues, including ligaments, make up joints, which connect some bones.
Bone constantly changes as new bone forms and old bone dissolves. To make new bone, the body deposits calcium into the cartilage. Some of the cartilage stays at the ends of bones to make joints.
Many types of cancer that start in other organs of the body can spread to the bones. These are sometimes referred to as metastatic bone cancers, but they are not true bone cancers.
Osteosarcoma risk factors
The cause of osteosarcoma, or bone cancer, is unknown, and it usually does not run in families. However, certain things seem to put children at a higher risk of developing osteosarcoma:
- Age: Osteosarcoma, or bone cancer, is most common in people between 10 and 30 years old, particularly teenagers in rapid growth cycles or “growth spurts.”
- Height: Most children with osteosarcoma are tall for their ages.
- Gender: More males than females develop the disease.
- Race: African Americans have a slightly higher risk of osteosarcoma.
- Previous radiation therapy
- Non-cancer bone diseases including Paget's disease and osteochondromas
- Rare inherited cancer syndromes, including, Li-Fraumeni, Rothmund-Thompson, and the RB1 gene mutation, which causes retinoblastoma
- Other rare genetic conditions, including Bloom syndrome and Werner syndrome
Osteosarcoma is rare, and not everyone with risk factors gets the disease. However, if you are concerned about your child’s risk for bone cancer, you should talk to his or her doctor.
Some cases of osteosarcoma can be passed down from one generation to the next. Genetic counseling may be right for you. Learn more about the risk to you and your family on our genetic testing page.