IDH2 and cholangiocarcinoma: IDH1/R132 and IDH2/R172 are commonly found in gliomas, cholangiocarcinomas, and chondrosarcomas, with a higher frequency of IDH1/R132 mutation occurring in these cancers (58%–90%, 40%–50%, and 50%–60% respectively) compared to IDH2/R172 (3%–5%, 5%–10%, and 10%).