IDH1 and IDH2 are frequently mutated in low-grade gliomas (grade 2–3) and secondary glioblastomas (70 to 90% of patients with glial tumours harboured an IDH mutation, mainly mIDH1) [6,7], acute myeloid leukaemia (AML, 15 to 20% of patients presented IDH mutations, with equal repartition between both isoforms) [2,8], chondrosarcoma (CHS, 50% of patients with central and periosteal CHS presented IDH mutations, mostly in IDH1) [9,10], intrahepatic cholangiocarcinoma (10 to 20%), and other tumours with lower frequencies (e.g., prostate cancer or angioimmunoblastic T-cell lymphoma) [11]. The gene discussed is IDH2; the disease is central nervous system cancer.