Giant cell tumor of the bone (GCTB) is usually a benign, locally aggressive tumor with metastatic potential. Histogenesis of GCTB is unknown and a correlation has not been found between histologic and clinical course. For this reason, many authors consider its prognosis unpredictable. Lung metastasis after GCTB treatment is well known and generally has unfavorable outcome, despite varied chemotherapy regimens. Denosumab, which inhibits RANK-RANKL interaction, is a new, promising actor among targeted therapeutic agents for GCTB. In this report, we emphasize on early rapid response to denosumab in metastatic GCTB.