CDKN2A and astrocytoma (excluding glioblastoma): For example, in an IDH-wildtype diffuse astrocytic tumor, the presence of TERT promoter mutation, EGFR gene amplification, or + 7/ − 10 chromosome copy number changes, is sufficient to diagnose IDH-wt Glioblastoma, grade 4, and the presence of CDKN2A/ B homozygous deletion results in a WHO grade 4 IDH-mutant Astrocytoma (Level IV-A).