IDH1 and anaplastic oligoastrocytoma: A study in India also showed that the highest percentage of IDH1 mutation cases was seen in grade II diffuse astrocytoma (70%), compared to grade III anaplastic astrocytoma (33.33%), grade IV glioblastoma multiforme (GBM) (13.04%), grade II oligoastrocytoma (50%), anaplastic oligoastrocytoma (66.67%), and oligodendroglioma grade II (70%) (Devi et al., 2018).