Research continues to reveal genetic alterations that disrupt the physiological process, including H3F3A mutations in giant cell tumour of bone [63], and germline mutations in the zinc finger protein 687 (ZNF687) and PFN1 genes both resulting in multiple giant cell tumour-like lesions arising on a background of Pagetic bone disease [64–66]. The gene discussed is PFN1; the disease is bone Paget disease.