IDH1 and glioblastoma: GBM is now defined as a diffuse astrocytic glioma with neither mutations in the IDH or histone H3 genes, and is characterized by microvascular proliferation and/or necrosis, and/or one or more of three genetic parameters: telomerase reverse transcriptase (TERT) promoter mutation, epidermal growth factor receptor (EGFR) amplification, or combined gain of entire chromosome 7 and loss of entire chromosome 10 (1).