Genomic sequencing has shown that intrahepatic CCA often displays an increased frequency of mutations in genes encoding isocitrate dehydrogenase (IDH, IDH1, IDH2) and Kirsten rat sarcoma 2 viral oncogene homolog (KRAS), fibroblast growth factor receptor (FGFR) 2 gene fusion events, and tumour protein p53 (TP53) mutations whereas extrahepatic CCA often shows an increased frequency of mutations in KRAS and TP53 [8, 9]. The gene discussed is IDH2; the disease is cholangiocarcinoma.