IDH1 and oligodendroglioma: Targeted sequencing of IDH1 and IDH2 in 445 central nervous system tumors revealed IDH1/2 mutations in 90% of cases of diffuse astrocytoma (grade II), 84% of oligodendroglioma (grade II), 73% of anaplastic astrocytoma (grade III), 94% of anaplastic oligodendroglioma (WHO grade III), and 85% of secondary GBM (grade IV) (Yan et al., 2009).