Bountiful Problems with Giant Cell Tumors of Bone

Giant Cell Tumors of Bone (GCTB) are a class of non-cancerous tumors that occur most frequently in the long bones of the body. They often appear in much younger populations than most tumors, usually when patients are 30-50 years old (van der Heijden, 2014). In a normal bone three types of cells are commonly found: osteoblasts to build the bone matrix, osteoclasts to break down the bone matrix, and osteocytes which are a type of regulatory cell. With GCTB, a mutation occurs in one a cell, often one located at the metaphysis of a long bone – where the bulbous “end” meets the narrower “shaft” (van der Heijden, 2014). The mutation leads the cell to grow much larger than normal, divide rapidly, and develop a great number of nuclei (up to 50!) (van der Heijden, 2014). The mutated cells begin expressing many of the same cell-surface proteins that osteoclasts do like Cathepsin K and so degrade the bone around them, making room for the tumor to grow (van der Heijden, 2014). This can lead to fractures as the strength of the bone decreases. The expansion of the tumor can also lead to swelling in the area. In addition to breaking down existing bone, GCTB also contain a large amount of collagen-like fibrous tissue (van der Heijden, 2014). This material does not become mineralized with calcium like it normally should, leaving the inside of the affected bone soft and at risk for necrosis (van der Heijden, 2014). Though GCTB are benign tumors, they are aggressive. Though rare, additional tumors may develop in the axial skeleton – usually the sacrum, but sometimes in the ribs or vertebrae (van der Heijden, 2014). In this case, treatment can become complicated. Surgery is the most common treatment; a window is cut into the bone and the tumor is scraped out before the cavity is packed with either a bone graft or bone cement (van der Heijden, 2014). In cases where surgery could cause too much damage drugs like bisphosphonates or denosumab can be prescribed which will inhibit the activity of osteoclasts, inhibiting the tumor as well and strengthening the bone by allowing osteoblasts to begin to make repairs at the site of the tumor (van der Heijden, 2014). Radiation is also a treatment option, but it does come with a higher risk of tumor recurrence than the previously mentioned method (van der Heijden, 2014).

 

van der Heijden, L, et al. 2014. The Clinical Approach Toward Giant Cell Tumor of Bone. The Oncologist, 19(5): 550-561. 10.1634/theoncologist.2013-0432