In human grade II/III gliomas (35, 36, 74, 76, 180), secondary glioblastomas (127), AML (16, 60, 103, 144), cholangiocarcinoma, chondrosarcoma (2), and in other cases of different tumor types (20, 54, 135, 192), heterozygous somatic missense mutations were found in IDH1 arginines of the catalytic site, such as (bold for most abundant) R132H/C/L/S and R100Q, or IDH2 arginines, such as R140Q/G/W/L and R172K/G/M/Q/T/S (20, 180) (Fig. 2). The gene discussed is IDH2; the disease is cholangiocarcinoma.