IDH1 and oligodendroglioma: With this approach, the majority of LGG can be assigned to one of the three mayor classes: IDH-mutant astrocytoma, IDH-mutant and 1p/19q-codeleted oligodendroglioma and IDH-wildtype gliomas which commonly demonstrate similar genetic alterations of glioblastoma and the associated poor prognosis (Fig. 1).