CDKN2A and glioblastoma: Together with IDH mutation, alterations in ATRX (16.1%) and TP53 (44.9%) are characteristic of diffuse astrocytoma, IDH mutant,26 with concurrent CDKN2A/B loss indicating WHO grade 4 astrocytoma.27EGFR amplification (23.1%) is enriched in IDH-wildtype glioblastoma.