IDH1 and astrocytoma (excluding glioblastoma): Given the similar prognostic outlook for IDH-mutant grade 2 and 3 astrocytomas, the recent literature tends to classify these together as “diffuse low-grade astrocytomas.” Conversely, the practice of aggregating “high-grade astrocytomas” (grades 3 and 4) is now advised against due to the distinct molecular profiles and clinical trajectories of IDH-mutant grade 3 astrocytomas compared to IDH-wild-type grade 4 astrocytomas, such as glioblastoma [19,20].