A giant cell tumor is a rare, abnormal growth of tissue which generally forms around the end of a long bone, most commonly the knee. The tumor is called giant because it looks very large under a microscope, and is made up of cells with more than one nucleus. Most of these are benign, though in rare cases they can be cancerous.
The most common location for a giant cell tumor is at the end of either the tibia or femur in the knee, though they are also found in the shoulder, wrist and spine. These cells act as osteoclasts, or cells that destroy and absorb bone. If the tumor is allowed to grow unchecked, it will weaken the bone and can lead to fractures.
The tumors are usually discovered because a patient goes to the doctor complaining of pain and swelling in the joint. An X-ray or magnetic resonance imaging (MRI) scan can confirm the diagnosis and reveal the extent of the growth. Giant cell tumors usually occur in young adults, and are slightly more common among Asians.
The primary treatment for a giant cell tumor is to remove it surgically before it can cause extensive bone loss. If the destruction of the bone is severe, cement may be applied to the area to replace the lost tissue and strengthen the joint. A biopsy is also done on the tumor to confirm that it is not malignant. In those rare cases when cancer is detected, radiation is recommended as post-operative treatment.
Whenever a giant cell tumor is discovered, it is important to do a computerized tomography (CT) of the chest to make certain that the tumor has not metastasized to the lungs. If caught in time, the lung can be treated as well, and the prognosis for a complete recovery is good. In a small percentage of cases, the tumor may reoccur, generally within the first three years. It is recommended that a patient return for regular checkups for a period of time to make certain the tumor does not reoccur.
A soft tissue giant cell tumor may also grow in the tendon sheath, or the membrane layer which surrounds a tendon. These tumors are composed of fibrous tissues and most commonly occur in the hands or feet. These also occur in young adults, though they are much more likely to be found in women than in men. A tendon sheath giant cell tumor is almost always benign, and generally painless. If the tumor is large enough to put pressure on the nerves, however, it may cause numbness to the nearby digits.
In cases where the tumor is particularly difficult to reach surgically, it may be treated with radiation. While this treatment is effective in destroying the tumor, it can result in the formation of cancer. Consequently, this option is used sparingly. After surgery patients are frequently given physical therapy to strengthen and stabilize the muscles and tendons surrounding the affected joint.