Kato I, et al. - Authors enquired regarding the histopathological features and H3 histone family member 3A gene (H3F3A) mutation status of giant cell tumour of bones (GCTBs) treated with denosumab in biopsy-diagnosed patients with GCTB, who underwent curettage following neoadjuvant denosumab therapy. All post-therapy lesions persistently constituted several G34W+ cells and harboured H3F3A mutations. RUNX2+ mononuclear cells appeared to coexpress G34W in pre-therapy and post-therapy lesions disclosed via immunofluorescence double staining. An effective decrease was achieved in the number of osteoclastic cells in GCTBs through denosumab therapy. Nonetheless, the neoplastic cells with H3F3A mutation survived denosumab treatment, while undergoing dramatic histological changes in response to this agent.