Thus, three major subtypes of GBM have been identified [14,15,16,17]: (i) the classical or proliferative subtype with EGFR amplification, deletion of the CDKN2A site (coding for p16INK4A and p14ARF), activation of the RB pathway, wild-type IDH1, and TP53 genes; (ii) the mesenchymal subtype with deletion of NF1, activation of the AKT pathway, and mutation in PTEN; (iii) the proneural subtype with amplification of PDGFRA and mutations in IDH1 and TP53. Here, RB1 is linked to glioblastoma.