GBs with mutations in the IDH1 gene (IDH1-M-GB), presently designated as Astrocytoma, IDH mutant, CNS WHO Grade 4 [52], which account for approximately 5% of GBs [53,54], are molecularly, biologically and behaviorally distinct from those without those mutations. This evidence concerns the gene IDH1 and astrocytoma (excluding glioblastoma).