IDH1 and glioblastoma: When comparing subtypes based solely on RNA expression, oligoneural precursors correspond to the proneural GBM subtype due to mutations in isocitrate dehydrogenase 1 (IDH1), mesenchymal neural precursors correspond to the mesenchymal GBM subtype due to mutations in NF1, and radial glia may correspond to the classic GBM subtype due to high levels of EGFR.