Histological features of dual-genotype gliomas in this study. a Primary moderately cellular infiltrating glioma from Case #1. At tumor recurrence, cells showed greater degrees of atypia and nuclear pleomorphism. Both primary and recurrent tumors were mitotically active without microvascular proliferation or necrosis. IHC was negative for IDH1-R132H, with ATRX loss, and overexpression of p53. b Case #2 demonstrated a low to moderately cellular infiltrating glioma with low mitotic activity. By IHC, the tumor was positive for IDH1-R132H, with loss of ATRX expression, and overexpression of p53