IDH1 and glioma: The authors showed that combining IDH1/2 mutation, 1p/19q codeletion and mitotic index (4/1000 tumor cells as cut-off) could stratify lower-grade gliomas into four prognostic groups, with 1p/19q codeletion identified tumors with better prognosis in IDH1/2 mutated group and mitotic index >4 identified tumors with poorer prognosis in IDH1/2 wild-type group [37].