IDH1 and astrocytoma (excluding glioblastoma): As IDH1/2 mutation status predated the knowledge of astrocytic tumor prognosis, homozygous deletion of CDKN2A/B was further proposed to be related to a poorer prognosis in patients with astrocytoma, IDH‐mutant, Grade 4.8, 45, 46, 47, 48, 49