IDH1 and glioblastoma: Modern clinical genetic testing in glioblastoma has led to further improvements in the classification of glioblastoma into several molecular subgroups, which were found to have prognostic and potentially therapeutic significance.7 Two molecular features with particularly significant clinical implications are the isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) gene mutations and O6-methylguanine-DNA-methyltransferase (MGMT) promoter methylation.