IDH1 and intrahepatic cholangiocarcinoma: This is in accordance with a report by Delahousse et al. including 8 patients with IDH1-mutated intrahepatic cholangiocarcinoma and 9 patients with wild-type IDH1 intrahepatic cholangiocarcinoma, which proposed a D/L-2HG ratio cutoff of 4.9 [49].