IDH mutant gliomas have a distinct biology that is associated with a superior prognosis compared to adult-type gliomas that are IDH wildtype.2 Clinically, patients with IDH-mutated tumours have improved overall survival and progression-free survival compared to IDH wild-type tumours.3–6 IDH mutation status therefore appears to be closely linked to tumour behaviour and may be more important for prognostication than grade.2 This evidence concerns the gene IDH2 and glioma.