IDH1 and oligodendroglioma: In the 2021 WHO classification, however, several molecular alterations have been included: EGFR amplification, TERT promoter mutation and/or +7/-10 signature for glioblastoma, IDH-wild-type; and homozygous deletion of CDKN2A/B for astrocytoma, IDH-mutant, grade 4 and for oligodendroglioma, IDH-mutant and 1p/19-codeleted, grade 3 (5).