IDH1 and oligodendroglioma: On the other hand, diffuse astrocytomas (IDH mutant and 1p19q intact) and oligodendrogliomas (IDH mutant and 1p19q co-deleted) belong to WHO grades II and III, which represent "lower-grade gliomas" (LGGs) in The Cancer Genome Atlas (TCGA) [1,2,3,4].