Typically occurring in adults between 20 and 40 years of age, giant cell tumors of the bone (GCT) is a rare, yet aggressive, non-cancerous tumor. GCT is hardly ever seen in children or in adults past the age of 65. These tumors occur in about one person per million each year.
GCTs are named for the way they appear under a microscope. When viewed from this vantage point, a plethora of “giant cells” is visible, formed by the fusion of many individual cells into a single, larger one.
While most bone tumors are found in the flared portion close the ends of the long bone, the giant cell tumor is usually found in the end portion of the long bones next to the joints. They frequently present around the knee joint in the lower end of the femur, or thigh bone, or in the upper end of the tibia, or the shin bone. Other locations where GCTs can be found include the wrist, the hip, the shoulder, and the lower back. In the rarest of instances, this type of tumor may possibly spread to the lungs.
Occurring spontaneously, giant cell tumors are usually not understood to be associated with any type of traumatic event, diet, or certain environmental factors. These tumors are not genetic, either, although in rare cases, they can be associated with hyperparathyroidism.
The first noticeable symptom of a giant cell tumor is pain in the location of the tumor. The patient may notice pain with any movement of a nearby joint. Typically, the pain will increase as the patient’s activity increases, and will decrease in times of rest. While the pain is generally mild at first, it will progressively increase in intensity.
In some instances, the tumor may weaken the affected bone and cause it to break, alerting the patient to sudden and severe pain. At other times, the patient might notice a mass or swollen area that may not necessarily cause any pain.
GCTs will appear on x-rays as destructive lesions next to a joint. Sometimes the bone near the location of the tumor will be expanded or it may be surrounded by a thin rim of white bone, either complete or incomplete. An MRI or a CT scan can help the doctor to evaluate more specifically the area that is affected.