The World Health Organization (WHO) 2021 classification of CNS tumours incorporates molecular parameters alongside histology. Grade II diffuse astrocytoma in an adult is now classified as IDH-mutant. The presence of IDH mutation in a glioma confers:
- A Worse prognosis compared to IDH-wildtype glioblastoma
- B Better prognosis compared to IDH-wildtype tumours at equivalent histological grade, with median survival significantly longer ✓
- C No prognostic significance; only histological grade matters
- D Resistance to temozolomide chemotherapy
Explanation
IDH1/IDH2 mutations are powerful positive prognostic markers in diffuse gliomas. IDH-mutant grade II–III astrocytomas and oligodendrogliomas have substantially longer median survival (7–15 years) compared to IDH-wildtype tumours such as glioblastoma (median survival ~15 months). IDH mutation leads to production of 2-hydroxyglutarate (oncometabolite) causing epigenetic reprogramming (CpG island methylator phenotype — CIMP), which is associated with better chemotherapy and radiotherapy response. Temozolomide is actually more effective in IDH-mutant/MGMT-methylated tumours.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.