Stratification of glioblastoma is challenging because these tumors display complex multilayered inter- and intratumoral heterogeneity.2,3 Current clinical stratification methods include extent of resection, Karnofsky Performance Score (KPS), age, O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation, and isocitrate dehydrogenase 1 (IDH1) mutation, none of which captures the heterogeneous landscape of glioblastoma.4–9 Modern “omic” technologies, such as high-throughput genomic, transcriptomic, and proteomic profiling, enable new approaches for tumor subset identification. The gene discussed is IDH1; the disease is glioblastoma.