Osteosarcoma

What Is It?

Osteosarcoma is the most common type of cancer to arise from bone cells, accounting for more than 50 percent of malignant bone tumors in adults and children in the United States. It typically appears as a mass of abnormal bone or unmineralized bone (osteoid) in an arm or leg, most commonly near the knee (50 percent of cases) or near the shoulder (25 percent of cases). Less often, the tumor develops in the pelvic bones, jaw or ribs, but only rarely in the fingers or toes (fewer than 1 percent of cases). At the time of diagnosis, 10 percent to 20 percent of osteosarcomas already have (spread to another site ( metastasized ), usually to the lungs.

Overall, osteosarcoma is a rare cancer that strikes only two in every 1 million people in the United States annually, occurring equally in all races. About 60 percent of osteosarcomas develop in people between the ages of 10 and 20, most often during the growth spurt of adolescence. An additional 30 percent of osteosarcomas strike adults between the ages of 40 and 50, more commonly men than women. Young people are at higher-than-average risk for developing an osteosarcoma if they suffer from retinoblastoma or Li-Fraumeni syndrome. Adults are at higher risk if they have a history of Paget's disease or radiation therapy for cancer.

Symptoms

Symptoms include persistent pain and swelling in an arm or leg, especially near the knee or shoulder. This pain may occur at rest, and it may even awaken the person from sleep. It may be mistaken initially for a sprain or some other sports injury, particularly in active teen-agers.

In addition, a firm lump on an arm or leg may be present, sometimes with local tenderness.

Diagnosis

Because osteosarcoma is very rare, your doctor usually will ask questions that are related to more common causes of pain and swelling in the limbs, such as sports injuries or arthritis. The true cause of your symptoms may not be known until the doctor orders an X-ray of the area.

After reviewing your symptoms, your doctor will perform a thorough physical examination with special attention to the painful area. Your doctor will check the affected area for warmth, swelling, tenderness, limitation of motion and any signs of joint swelling or joint fluid. This physical examination will be followed by an X-ray of the area, and, sometimes, blood tests. In most cases, the blood tests will be normal, except for high levels of serum alkaline phosphatase in 45 percent to 50 percent of patients. However, the X-ray typically shows characteristic abnormalities suggesting cancer.

Once your doctor has found X-ray evidence of a bone tumor, he or she will refer you to a major medical center that has the facilities, personnel and experience to treat bone cancer. There, you may have a magnetic resonance imaging (MRI) scan of the affected area to determine how far the tumor has invaded local structures, particularly nerves, blood vessels and any nearby joint. You also may have X-rays and a radionuclide bone scan to check for any metastases (spread) to your lungs or to other sites, especially other bones). After these tests are complete, you will have a biopsy to confirm the diagnosis of osteosarcoma. The exact location and surgical approach of this biopsy will be determined by your surgeon.