These subgroups can be additionally linked to characteristic morphological appearances like sarcomatous features in oligosarcomas [16], mutation profiles such as hypermutation and mismatch-repair-deficiency in primary mismatch-repair-deficient IDH‐mutant astrocytomas (PMMRDIAs) [17] or special localisations as for infratentorial IDH-mutant astrocytomas [2]. This evidence concerns the gene IDH1 and astrocytoma (excluding glioblastoma).