In contrast, IDH-mutant glioblastomas, which have recently been re-named as astrocytoma, IDH-mutant, WHO grade 4 [3], are less common, typically occur in patients younger than 50 years and may develop from pre-existing IDH-mutant lower grade astrocytomas [2, 4]. Here, IDH1 is linked to astrocytoma (excluding glioblastoma).