IDH2 and oligodendroglioma: To do this, we identified a group of astrocytomas, IDH-mut, grade 3 and grade 4, and oligodendroglioma, IDH-mut, grade 3 (n = 88), with a high level of the HIF-1α hypoxic marker and a group of the same tumor types (n = 80) with a low expression of HIF-1α marker (Figure 4e).