A giant cell tumor is one that is made up of a large number of benign (non-cancerous) cells that form an aggressive tumor - usually near the end of the bone near a joint. The location of a giant cell tumor is often in the knee, but can also involve the bones of the arms and the legs, or the flat bones such as the sternum (breastbone) or pelvis. The tumor is often coated by new bony growth. It causes pain, restricts movement, and is usually cancerous.
Giant cell tumors most often occur when skeletal bone growth is complete. They are most prevalent after age 20 and are rare after age 55. It is rare, but these tumors can occur in children. At any age, they are more commonly seen in females than males.
Giant cell tumors occur in approximately one person per million people per year. They most frequently occur around the knee joint in the lower end of the thighbone (femur) or the upper end of the shinbone (tibia). Other common locations include the wrist (lower end of the lower arm bone), the hip (upper end of the thighbone), the shoulder (upper end of the upper arm bone) and lower back (connection of the spine and pelvis). The bone involved is generally tender. There may be swelling in the area around it.
While the exact cause of giant cell tumors remains unknown, in some cases, they have been linked to Paget's disease. Paget's disease of the bone is a chronic bone disorder in which bones become enlarged and deformed. Giant cell tumors of bone occur spontaneously. They are not known to be associated with trauma, environmental factors or diet. They are not inherited. In rare cases, they may be associated with hyperparathyroidism.
The first symptom most patients notice is pain in the area of the tumor. There may be pain with movement of a nearby joint. Pain generally increases with activity and decreases with rest. Pain is usually mild at first, but it progressively increases. Occasionally the bone weakened by the tumor may break and cause sudden onset of severe pain. Sometimes patients will notice a mass or swollen area that may not be painful. GCT is given its characteristic appearance by the constant finding of a large number of these cells existing in a typical background. Most bone tumors occur in the flared portion near the ends of long bone (metaphysis), but GCT occurs almost exclusively in the end portion of long bones next to the joints (epiphysis). In rare cases, this tumor may spread to the lungs.
The goal for treatment of a giant cell tumor is to remove the tumor and prevent damage to the affected bone. Surgery has proven to be the most effective treatment for giant cell tumors. Radiation therapy is a non-surgical treatment option that has proven effective. However, this can result in the formation of cancer in as many as 15 percent of patients who receive it. Therefore, radiation therapy is used only in the most difficult cases where surgery cannot be performed safely or effectively. Embolization and treatment with interferon is generally reserved for those tumors that are difficult to remove surgically or in situations where the tumor keeps returning despite treatment or if it spreads.