IDH1 and glioblastoma: Isocitrate dehydrogenase 1 (IDH1) mutations, which are associated with more favorable outcome, represent a new tumor group termed ‘adult-type, diffuse glioma, IDH-mutant, astrocytoma, grades 2-4’, while glioblastoma is now reserved to the ‘adult-type, diffuse glioma, IDH1 wildtype’ (3–6).