IDH1 and glioblastoma: Amongst numerous genetic alterations, the most striking changes in gene expression used to define each subtype are found in platelet derived growth factor receptor alpha (PDGFRA)/IDH and p53 mutations for PN, epidermal growth factor receptor (EGFR) for CL, and neurofibromatosis type 1 (NF1) for MES GBM [34,99].