Giant cell tumor (GCT) is a rare, usually benign but locally aggressive neoplasm. Recent studies suggest new approaches in light of the elucidation of molecular pathways in bone. The osteolytic nature of GCT is caused by the receptor for activating nuclear factor-kB ligand (RANKL) associated osteoclasts. Denosumab is a monoclonal antibody that affects GCT through RANKL and it prevents normal and neoplastic osteolysis. The aim of this study is to evaluate the histopathologic alterations due to denosumab treatment and the efficiency of this drug in GCT therapy.