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 The gene discussed is IDH1; the disease is central nervous system cancer.