Based on the 2021 WHO criteria, the 79 tumors were reclassified into 27 oligodendrogliomas (16 CNS WHO grade 2 and 11 CNS WHO grade 3) and 52 IDH-mutant astrocytomas (16 CNS WHO grade 2, 19 CNS WHO grade 3, 17 CNS WHO grade 4), Additional file 1: Figure S1A. This evidence concerns the gene IDH1 and oligodendroglioma.