We may think of bone as hard or "dead," but it is really a living tissue made up of living cells. There are several types of cells in our bones:

• Osteoblasts make the matrix of the bones, that is, the connective tissue and minerals that give the bones strength.

• Osteoclasts prevent too much bone matrix from building up. These cells help bones keep their shape. They also help control the amount of minerals in the blood.

• Bone marrow (found in some bones) contains fat cells and, most importantly, cells that make blood cells. All blood cells are made here.

There are 2 main types of bones: flat bones and long bones. Flat bones, such as those of the skull, help to protect organs like the brain. Long bones support the arms and legs.

Osteosarcoma

Osteosarcoma is the most common type of cancer that starts in the bone. The cells that form this cancer make bone, but this cancerous tissue of osteosarcoma is not as strong as normal bones.

Like other cancers, osteosarcoma can spread beyond the bone into nearby tissues. Cancer cells can also break away from the main tumor and spread through the bloodstream to other bones or to the lungs or other organs. This process is called metastasis.

Osteosarcoma often starts near the ends of the long bones in the legs, especially around the knee, the part of the thigh bone next to the knee, and the part of the lower leg bone next to the knee. The arm bone near the shoulder is the second most common place for this cancer to start. But it can start in other bones, too. Cancer that starts in places like the pelvis, shoulder, or jaw (as well as places where it's hard to do surgery) tends to have a poorer outcome.

Ewing tumor

Ewing tumor is the second most common kind of bone cancer in children. It is described in another American Cancer Society document which you can get by calling our toll-free number.

Many bone tumors are not cancer. These are called benign (be-nine) bone tumors. Benign bone tumors do not spread to other parts of the body and most of the time they are not dangerous. Sometimes the doctor needs to take a sample of the tumor (a biopsy) to tell whether it is cancer or benign.

Subtypes of osteosarcoma

There are several subtypes of bone cancer. The subtype is based on how the cancer looks on x-rays and under the microscope. Some subtypes have a much better outlook for survival than others.

Osteosarcomas can be grouped as low grade, intermediate grade, or high grade. If the tumor has few dividing cells, it is called a low-grade osteosarcoma. If it has many dividing cells and a lot of dead cells in the center, it is high grade.

The grade is important because it tells the doctor how likely the cancer is to spread to other parts of the body. Low-grade tumors need to be removed, but the patient usually does not need chemo. These tumors have a good outlook. Patients with high grade tumors need surgery and chemo. Most osteosarcomas in children are high grade. If you or your child has bone cancer, ask the doctor to explain the subtype and what that means for treatment.

Last Medical Review: 03/20/2007
Last Revised: 03/20/2007