Giant Cell Tumor of Bone Giant cell tumor of bone (GCT) is a rare, aggressive non-cancerous (benign) tumor. It generally occurs in adults between the ages of 20 and 40 years. Giant cell tumor of bone is very rarely seen in children or in adults older than 65 years of age. Giant cell tumors occur in approximately one person per million per year.                            X-ray of a typical giant cell tumor in the end of the radius bone. Giant cell tumors are named for the way they look under the microscope. Many "giant cells" are seen. They are formed by fusion of several individual cells into a single, larger complex. Many bone tumors and other conditions (including normal bone) contain giant cells. Giant cell tumor of bone 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 giant cell tumor of bone 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. 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. Symptoms 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. 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. Diagnosis Giant cell tumors appear on X-rays as destructive (lytic) lesions next to a joint. Occasionally, the involved area of bone can be surrounded by a thin rim of white bone that may be complete or incomplete. The bone in the area of the tumor is sometimes expanded. Often a doctor may use magnetic resonance imaging (MRI) and computed tomography (CT) scans. These can help better evaluate the area of involvement. A bone scan generally shows a "hot spot" in the bone where the tumor is. An X-ray or CT scan of the chest will often be done to look for possible spread to the lungs. Treatment If not treated, these tumors will continue to grow and destroy bone. Surgery has proven to be the most effective treatment for giant cell tumors. Nonsurgical Treatment Radiation therapy is a nonsurgical 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. Some centers have reported successful treatment of giant cell tumors with embolization, a process where the blood vessels supplying the tumor are occluded by means of a catheter threaded through the main arteries. Blocking the blood supply to the tumor can cause it to shrink and even disappear because the tumor loses its source of nutrition. Clinical trials of a drug called interferon are currently underway. This drug works by interfering with the ability of the tumor to grow new blood vessels. Because tumors require an ever-increasing blood supply to grow, interferon may also cause the tumor to shrink or even disappear. Like radiation therapy, embolization and treatment with interferon are 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. Surgical Treatment Scooping out the tumor (curettage) is generally performed. This techniques cause a hole in the bone that can be filled with a bone graft. The bone may be taken from other parts of the patient's own body (autograft) or from a cadaver (allograft). If treatment is limited to curettage and bone grafting alone, the tumor may come back (recur) up to 45 percent of the time. The use of bone cement rather than bone graft results in a lower rate of recurrence. Enhancing the curettage with a high-speed burr or with the use of agents such as liquid nitrogen, hydrogen peroxide, or phenol, followed by placement of bone cement decreases the recurrence rate to 10 percent to 29 percent. More complex tumor removal and reconstruction is sometimes necessary in situations where the tumor has caused excessive damage or recurred. In the rare cases where the tumor has spread to the lungs, surgical removal of the tumor in the lungs results in cure 75 percent of the time.