IDH1 and astrocytoma (excluding glioblastoma): Accordingly, the latest 2021 edition of WHO classification has officially adopted CDKN2A/B homozygous deletion as the sole molecular feature in IDH-mutant astrocytoma, with the recommendation of an integrated and layered diagnosis: astrocytoma, IDH-mutant, CNS WHO grade IV, CDKN2A/B homozygous deletion [3,8] (Table 1).