Although they were thought to be virtually exclusive in glioma [11,14], further mutational analyses revealed IDH1 and IDH2 mutations, as well as IDH2 Arg140 mutations, in various cancer types such as myeloid neoplasia, chondrosarcoma, cholangiocarcinoma, and prostate cancer [2,15]. The gene discussed is IDH2; the disease is cholangiocarcinoma.