IDH2 and oligodendroglioma: Table 1 also shows grouping of the 1960 cases adopting the WHO 2016 classification of glial tumours into five categories (Astrocytoma with IDH mutation, IDH wild-type astrocytoma, Oligodendroglioma with 1p/19q co-deletion, GBM with IDH mutation and IDH wild-type GBM) (Supplementary Table 2 [Online Resource 1]).