IDH1 and glioblastoma: They were first classified separately within the 2016 WHO Classification (as glioblastoma, IDH-mutant) and have been further distinguished as a separate entity within the recent 2021 WHO Classification, which removed the nomenclature glioblastoma entirely, terming them as astrocytoma, IDH-mutant, CNS WHO grade 4 [1,16,28,29].