IDH-mutant DGs are separated into oligodendrogliomas (grade 2 or 3, the presence of a 1p/19q codeletion being mandatory for diagnosis) and IDH-mutant astrocytomas (grade 2, 3 or 4) with most “lower-grade” DGs belonging to this category. Here, IDH1 is linked to astrocytoma (excluding glioblastoma).