The mutational status of the IDH1, IDH2, TP53, TERT, ATRX, H3F3A, and HIST1H3B genes allowed for the classification of 79% of the 648 diffuse gliomas analyzed into IDH-wild-type glioblastoma, IDH-mutant glioblastoma/diffuse astrocytoma, and oligodendroglioma, each subtype exhibiting diverse median overall survival (1.1, 6.7, and 11.2 years, respectively). Here, IDH1 is linked to oligodendroglioma.