Giant cell tumor is a fast-growing noncancer (benign) bone tumor that most commonly affects the knee, but can grow in any bone. It often grows near a joint at the end of the bone (epiphyses). It can also grow in flat bones, such as the breastbone and pelvis. Giant cell tumors are usually asymptomatic and only discovered when a bone scan or other imaging test is done for another reason. The most common symptoms are pain and swelling of the affected bone.
Giants cell tumors grow very fast and can weaken the bones in the area of the lesion. They are also prone to recurrence, especially in the knee. Giant cell tumors can also be linked to Paget disease of the bone, a long-term (chronic) condition in which bones become enlarged and misshapen due to abnormal calcium deposits.
It is thought that giant cell tumors are the result of a mutation in an immature osteoblast. Because they are so fast-growing, giant cells can overtake normal bone cells and replace them. Over time, this can lead to a bone spur and/or a hole in the bone that can be felt as pain and noticed by the patient.
The diagnosis is made by examining the patient and taking a small sample of the tumor to be tested. A biopsy can confirm the diagnosis of giant cell tumor and help determine how the tumor should be treated.
There are several different treatments for giant cell tumor. The most effective treatment is surgery to remove the tumor and surrounding tissue. This can be performed by curettage (scraping the bone with special instruments) or surgical excision. In some cases, a drug can be given to stop the growth of the tumor. This drug targets a specific receptor on the giant cells and decreases their activity. However, the tumor can recur after stopping the medication.
Giant cell tumors recur in 17%-25% of patients. The recurrence rate is higher in diffuse type giant cell tumor, which are more difficult to resect. Local recurrence can cause painful deformities, pathologic fracture, and loss of function. Bone grafting can improve the prognosis in these patients.
New pharmaceutical treatments for GCT have been introduced to reduce recurrence rates and improve clinical outcomes. Denosumab, a monoclonal antibody that blocks the interaction of RANKL with its receptor on osteoclasts, prevents bone resorption and inhibits tumor progression in GCT. Early studies show that it can be used in combination with neoadjuvant systemic therapy to facilitate intralesional surgery and reduce recurrence risk. However, further study is needed to confirm these findings.
