The 4 discrepant cases were IDH-wildtype infiltrating astrocytomas which by FISH all had average EGFR signals per nucleus > 4 (range 4.48–6.62) and ratio of EGFR signals/CEP7 signals (a centromeric probe) > 2 (range 2.1 -2.92). Here, IDH1 is linked to astrocytoma (excluding glioblastoma).