IDH2 and astrocytic tumor: Based on these findings, we first classified astrocytic tumors into IDH-mut and IDH-WT tumors and then defined IDH-mut tumors with ATRX-low as A1, IDH-WT tumors with high Ki-67 expression as A3, and grouped IDH-mut tumors with ATRX-high and IDH-WT tumors with low Ki-67 expression into A2 (Fig.4).