It is worth noting that mutations in FGFR4 are rare, but that Hatlen et al. identified gatekeeper mutations (V550M/L) and Hinge-1 (C552) mutations in the FGFR4 kinase domain from hepatocellular carcinoma patients after treatment with the selective FGFR4 inhibitor Fisogatinib (BLU-554) [40]. The gene discussed is FGFR4; the disease is hepatocellular carcinoma.