The recent World Health Organization (WHO) Classification of Tumors of the Central Nervous System (CNS) recommends stratification of IDH-mt glioma into WHO grade 2–4 for astrocytoma and grade 2–3 for oligodendroglioma based on their neuropathological features (Louis et al. 2021). The gene discussed is IDH1; the disease is astrocytoma (excluding glioblastoma).