Overview
Osteosarcoma is a primary bone cancer. This means the cancer starts in a bone rather than spreading to bone from another part of the body. Osteosarcoma begins in the cells that form bones. Osteosarcoma tends to happen most often in teenagers and young adults. But it also can happen in younger children and older adults.
Osteosarcoma is rare. Even so, it is the most common primary bone cancer in children, teenagers and young adults.
Osteosarcoma also is called osteogenic sarcoma.
Osteosarcoma can start in any bone. It's most often found in the long bones of the legs and sometimes the arms. Very rarely, osteosarcoma happens in soft tissue outside the bone. This is called extraskeletal osteosarcoma.
Osteosarcoma is different from other primary bone cancers because its cancer cells make immature bone, called osteoid. Ewing sarcoma is another bone cancer seen mostly in children and young people. But it has different tumor biology, and it is treated with a different combination of chemotherapy and local treatment.
Advances in the treatment of osteosarcoma have improved the outlook for this cancer. Children and adolescents treated for osteosarcoma may have side effects that last or develop months or years after treatment. Healthcare professionals often suggest lifelong monitoring for side effects after treatment.
Osteosarcoma
Osteosarcoma
Osteosarcoma is a kind of bone cancer. It most often starts in the long bones of the legs or the arms. But it can happen in any bone.
Types
There are several types of osteosarcoma. The type is based on where the tumor starts, in the bone or on the bone surface, and what the cancer cells and tumor tissue look like under a microscope.
- Conventional osteosarcoma. This is the most common type. It starts inside the bone and usually is high grade, meaning the cancer cells tend to grow and spread more quickly. Conventional osteosarcoma may be described as osteoblastic, chondroblastic or fibroblastic based on the tissue seen under a microscope. These subtypes are generally treated the same way.
- Telangiectatic osteosarcoma. This is a rare, high-grade type. It contains blood-filled spaces and can look different from conventional osteosarcoma on imaging.
- Parosteal osteosarcoma. This type grows from the outer surface of a bone. It usually is low grade and tends to grow more slowly than conventional osteosarcoma.
- Periosteal osteosarcoma. This type also grows on the surface of a bone. It is usually intermediate grade and often has tissue similar to cartilage.
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Symptoms
Osteosarcoma signs and symptoms most often start in a bone. The cancer most often affects the long bones of the legs and sometimes the arms. The most common symptoms include:
- Bone or joint pain. Pain might come and go first. It can be mistaken for growing pains.
- Pain related to a bone that breaks for no clear reason.
- Swelling or a growing lump near a bone. The lump may feel firm and may not move easily. It can be painful.
When to see a doctor
Make an appointment with a healthcare professional if you or your child has ongoing symptoms that worry you. Osteosarcoma symptoms are like those of many more common conditions, such as sports injuries. The health professional might check for those causes first.
Causes
It's not clear what causes osteosarcoma. Osteosarcoma develops when bone-forming cells undergo genetic changes. The exact changes that lead to the cancer are not fully understood.
As osteosarcoma grows, it can damage nearby tissue and spread to other parts of the body. The lungs are the most common site of distant spread. The cancer also can spread to other bones.
Risk factors
Most people with osteosarcoma don't have any known risk factors for the cancer. But these things can raise the risk of osteosarcoma:
- Certain conditions that run in families. These include hereditary retinoblastoma, Bloom syndrome, Li-Fraumeni syndrome, Rothmund-Thomson syndrome and Werner syndrome.
- Other bone conditions. These include Paget's disease of bone and fibrous dysplasia.
- Prior treatment with radiation therapy.
Complications
Osteosarcoma can spread from where it started to other areas. This is called metastatic osteosarcoma. Cancer that has spread can affect treatment options and outlook. Osteosarcoma most often spreads to the lungs, another part of the same bone or to another bone.
Prevention
In general, there is no way to prevent osteosarcoma. People with hereditary conditions should be monitored for the development of osteosarcoma and other cancers. People with Li-Fraumeni syndrome, which raises the risk of many cancers, should avoid radiation for the treatment of other cancers because radiation has a high risk of inducing osteosarcoma. These hereditary conditions are very rare, however.
Sept. 18, 2026