IDH1 and glioblastoma: The discovery of mutations of the Isocitrate Dehydrogenase (IDH) genes and of the DNA hypermethylation signature (Glioma CpG Island Methylator Phenotype: G-CIMP) has led to the definition of a distinct GBM subtype characterized by younger age and improved survival (2, 17, 18, 35) (Figure 2, N. 1).