It is noteworthy that a considerable progress has been achieved in molecular classification of GBM, which is now known to comprise several disease entities, such as proneural, neural, classical and mesenchymal tumors [146] (also recently re-classified as IDH1 mutant tumors and three subgroups of IDH1 wild-type GBMs—RTK I, RTK II and Mesenchymal) [2]. This evidence concerns the gene IDH1 and glioblastoma.