Bone cancer is an uncontrolled growth of abnormal cells within the bone. Bone provides structure to the body, protects internal organs, and produces and stores blood cells. Bone also acts as levers and braces for muscles to produce movement.

Bone tumors can be either benign (noncancerous) or malignant (cancerous). Both types can grow and compress normal bone tissue and absorb or replace it with abnormal tissue. Benign bone tumors, which are more common, do not spread and are rarely life-threatening.

The two main forms of cancer found in bone are primary bone cancer and secondary bone cancer. Primary bone cancer begins in the bone. Secondary bone cancer, or metastatic bone cancer, does not begin in the bone but has spread there from another area of the body. Secondary bone cancer often results from the spread of cancer from the lung, breast or prostate.

Primary cancer is not the same condition as secondary cancer. These forms of cancer can usually be distinguished from one another when their cells are examined under a microscope. For example, if bone cancer develops from metastasized breast cancer, the cells will look like breast cancer cells, not bone cancer cells. Treatment will vary based on where the cancer originated.

Primary bone cancer is rare and accounts for less than 0.2 percent of all cancers. It is much more common for cancer to spread to a bone from another site of origination. Types of primary bone cancers include:

• Osteosarcoma
• Chondrosarcoma
• Chordoma
• Fibrosarcoma and malignant fibrous histiocytoma
• Giant cell tumor of the bone

The exact cause of bone cancer has not been identified. Recently researchers have gained a greater understanding of how specific changes in DNA may cause bone cells to become cancerous. In addition, researchers have identified a number of factors that may make a person more likely to develop bone cancer, including retinoblastoma (a rare eye cancer of children), Paget’s disease and exposure to large doses of radiation.

A biopsy is required to diagnose primary bone cancer but may not be necessary to verify metastatic bone cancer. The procedure involves removing a sample of the tumor and examining it under a microscope. Once a diagnosis has been confirmed, the disease will be staged. Staging is the process of determining how far the cancer has spread and is necessary for physicians to plan treatment. The lower the stage, the earlier the disease has been identified and the better the prognosis for recovery.

After bone cancer is diagnosed and staged, a treatment plan will be recommended. Treatment methods are chosen based on the type, size, location, and stage of the cancer, as well as the patient’s age and general health. The main method used to treat bone cancer is often surgery. Other treatment options include radiation therapy and chemotherapy.

The American Cancer Society (ACS) predicts about 2,300 Americans will be diagnosed with primary cancer of the bones and joints in 2007. Primary bone cancers account for less than 0.2 percent of all cancers. Bone cancer can occur at any age, but approximately 30 percent of the cases develop in children and adolescents. The prognosis for patients diagnosed with bone cancer varies significantly based on the type of cancer and the extent metastasis. In 2007, primary bone cancer is expected to cause about 1,300 deaths.

Secondary bone cancer (cancer that has spread to the bone from another site) is more common than primary bone cancer. According to the ACS, almost all people who die of cancer (approximately 560,000 people per year) will have bone metastasis at some point during their illness.