According to this update, IDH-mutant astrocytoma (WHO grade IV), with CDKN2A/B locus homozygous deletion as molecular marker, previously classified as IDH-mutant GB [4,11,63], is now classified as “astrocytoma, IDH-mutant, WHO grade 4 and no longer as glioblastoma” [62,64]. This evidence concerns the gene IDH1 and glioblastoma.