IDH1 and anaplastic oligodendroglioma: In fact, the 2016 update to the WHO Classification of Tumors of the CNS has made this molecular change part of the diagnosis for the grade II/III “diffuse astrocytoma, IDH-mutant,” “anaplastic astrocytoma, IDH-mutant,” “oligodendroglioma, IDH-mutant and 1p/19q-codeleted” and “anaplastic oligodendroglioma, IDH-mutant and 1p/19q-codeleted.” Grade II “diffuse astrocytoma, IDH-wildtype” is a provisional entity given its rarity [8].