Giant cell tumor
Giant cell tumors are a relatively uncommon, yet very aggressive type of bone tumor. A giant cell tumor is generally considered to be benign (noncancerous) and usually begins near the ends of the bone. These are commonly seen in the femur (thighbone) and tibia (shinbone), but can also be found in the wrist, arm or pelvis. Only one out of every million people is struck with this disease, making it quite rare.
The tumor is named for the characteristic giant cells which comprise one of the cell populations that appears under the microscope. While these cells typically are not malignant (cancerous) in nature, on rare occasions they do have the possibility of spreading to the lungs. There is a very small chance of transformation to a malignant tumor. Giant cell tumors mostly are found in young adults from ages 20 to 40, and are typically not seen in children or the elderly. Without treatment, these tumors can continue to grow and destroy the surrounding bone, which makes treatment necessary.
While the exact cause of a giant cell tumor has yet to be determined, there are a few ideas about what could increase a person’s risk of developing it:
- Paget’s disease – This chronic bone disorder is directly associated with how the bone grows and functions. While the mechanism is not well understood, there is an increased incidence of giant cell tumor in patients with Paget’s disease.
- RANK-L – Expression of receptor activator of NF-kB ligand (RANK-L) may be responsible for the presence of giant cells within the tumor. However, while the namesake cells are often found in abundance, research indicates that another cell population actually is responsible for the tumor itself. The giant cells, which closely resemble the osteoclast cells that digest bone, in this condition are involved in the destruction of bone. Hence, this pathway has been a target for new pharmaceuticals for giant cell tumors of bone.
Depending on where the giant cell tumor is located, symptoms may vary. Generally speaking, people who have these tumors do experience some of the symptoms listed below. However, in rare cases, the tumor may remain asymptomatic (without symptoms), and therefore hidden in the body until a test performed for other reasons discovers it.
The following are the most common giant cell tumor symptoms. People react very differently to these tumors, so patients may have one or multiple symptoms:
- Pain at the nearest joint
- Visible swelling from a mass
- Unexplained bone fracture
- Reduced mobility near the joint
Giant cell tumor symptoms may be mistaken for those symptoms associated with other diseases. For this reason, it is important to see a doctor if there is any pain in the bone or joints.
Giant cell tumors appear most commonly in the bones. However, there are certain instances in which they become malignant and/or spread to other areas:
- Giant cell tumors of bone – This is the most common form of giant cell tumors, which are typically located near the ends of long bones. This tumor is generally considered benign, though locally aggressive. It is capable, in a small percentage of patients, of traveling to the lungs, despite being a benign tumor.
- Malignant giant cell tumor of bone – Though rare, giant cell tumors have the ability to transform to a malignant tumor. In such cases, they display the aggressive behavior of a high-grade sarcoma. Unlike the benign giant cell tumor of bone, these have a tendency towards malignant lung metastasis.
- Giant cell tumor of tendon sheath – Despite a similar name, this condition is entirely unrelated to giant cell tumor of bone. Giant cell tumor of tendon sheath is a benign tumor that results from proliferation of the lining of tendons. It is equivalent to a condition of the joints known as pigmented villonodular synovitis (PVNS).