IDH1 and oligodendroglioma: In a retrospective series of gliomas diagnosed according to the 2016 WHO classification by Wijnenga et al., the authors found that postoperative volume was associated with OS, with a strong detrimental effect of even small tumor remnants only in IDH-mutant astrocytomas, but not in IDH-mutant 1p19q codeleted oligodendrogliomas (22).