This applies to diffuse astrocytomas with IDH mutation showing a homozygous deletion of the CDKN2A or CDKN2B gene, and for glioblastomas with IDH wildtype showing at least one of three typical molecular alterations: EGFR gene amplification, TERT promotor mutation, +7/−10 chromosome copy number changes. The gene discussed is CDKN2A; the disease is diffuse astrocytoma.