IDH1 and oligodendroglioma: Similar data from Europe revealed that 72.7% of diffuse astrocytomas (WHO grade II) harbor IDH1 mutation, 64.0% in anaplastic astrocytomas WHO grade III, 82.0% in oligodendrogliomas WHO grade II, 69.5% in anaplastic oligodendrogliomas WHO grade III, 81.6% in oligoastrocytomas WHO grade II, and 66.1% in anaplastic oligoastrocytomas WHO grade III (Hartmann et al., 2009).