IDH2 and astrocytoma (excluding glioblastoma): Whether they are inherited or acquired, these mutations are frequently associated with high-grade histologic and molecular features and are often associated with progression in grade when acquired between sampling, but they may confer poor prognosis even when identified in IDH-mutant astrocytomas with no otherwise worrisome features, suggesting they may serve as a useful biomarker in certain circumstances [179, 200, 209].