IDH1 and oligodendroglioma: When analyzing OS according to the 2016 WHO classification by adding the NOS (Not Otherwise Specified) and NEC (Not elsewhere Specified) subtypes of the new WHO classification without taking into account other factors, OS was higher in patients with oligodendroglioma, IDH mutation and 1p19q codeletion (n = 28; median not reached with a median follow-up of 191 months), followed by those classified as oligodendroglioma NEC (n = 6; OS 353 months), those with IDH mutant astrocytoma (n = 39; OS 174 months), and those with IDHwt astrocytoma (n = 14; OS 116 months).