Previously, we have demonstrated that overall copy number variation (CNV), distributed across the entire genome, tends to increase with histologic grade in IDH-mutant astrocytomas [28], and IDH-mutant grade 2–3 astrocytomas with poor clinical outcomes have incongruously elevated overall CNV at the time of initial diagnosis [27, 29]. Here, IDH2 is linked to astrocytoma (excluding glioblastoma).