IDH1 and glioblastoma: The IDH1 wild type HGG tumours presently referred to as proper GBM, are further subclassified into classical (CL), mesenchymal (MES) and proneural (PN) subgroups in part depending on major genetic drivers of oncogenesis, particularly EGFR (CL), NF1 (MES), and PDGFRA (PN), as well as transcriptomic signatures and methylation patterns (54).