IDH2 and astrocytoma (excluding glioblastoma): MYCN amplification has been shown to be associated with shorter survival in patients with IDH-mutant astrocytomas (grades 2–4)75,93,96 The frequency of MYCN-amplification increases with WHO 2016 tumor grade (Table 3), and was relatively high (8%–12%) in 2 separate cohorts of grade 4 IDHmt astrocytomas.99,101