IDH2 and astrocytoma (excluding glioblastoma): While overall CNA levels tend to be significantly elevated in cases with either grade 4 histology or equivalent molecular features [150, 175], there is a subset of grade 2–3 IDH-mutant astrocytomas (approximately 15% of cases) in which incongruously elevated overall CNA levels are associated with dismal survival (progression-free survival (PFS) ≤ 12 months and overall survival ≤ 24 months), and this is true when selecting specifically for elevated overall CNA or poor clinical outcomes and excluding cases with other known high-grade molecular features [174–176].