Epigenetically based molecular classification of 932 adult diffuse primary gliomas (WHO grades II to IV) analyzed by our group uncovered the existence of three cohesive molecular subtypes of IDH mutant gliomas (Codel, G-CIMP-high, and G-CIMP-low) and four subtypes of IDH-wild-type gliomas (classic-like, mesenchymal-like, LGm6-GBM, and pilocytic astrocytoma [PA]-like) with characteristic patient outcomes. Here, IDH1 is linked to glioblastoma.