# The 2021 WHO classification of tumours of the central nervous system: a summary

Source: https://onco.cc/key-papers/paper-who-2021-cns-louis-neuro-oncology-2021/  
OnCo record `paper-who-2021-cns-louis-neuro-oncology-2021` (Key paper). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The fifth-edition brain tumour classification makes molecular markers such as IDH mutation, 1p/19q codeletion and methylation class central to diagnosis, renaming and regrading many tumours, including separating IDH-mutant astrocytoma from glioblastoma.

## Summary

Summary of the 2021 WHO classification of central nervous system tumours introducing integrated histological and molecular diagnoses, Arabic numeral grading within tumour types, new tumour types and families (paediatric-type diffuse gliomas, molecularly defined ependymomas and medulloblastoma groups), and grading of IDH-mutant astrocytoma up to grade 4 with CDKN2A/B deletion.

## Fields

- Kind: Key paper
- Last checked: 2026-09-17
- Journal: Neuro-Oncology
- Year: 2021
- DOI: 10.1093/neuonc/noab106
- Authors: Louis DN, Perry A, Wesseling P, et al.
- What it means: Every brain tumour page on this site uses these names and grades; a tumour called glioblastoma before 2021 may now be an IDH-mutant astrocytoma with a different outlook and treatment.
- Caveats: Requires molecular testing that is not available everywhere, leaving some diagnoses as not otherwise specified.

## Sources

- Neuro Oncol 2021: https://doi.org/10.1093/neuonc/noab106
- PubMed: https://pubmed.ncbi.nlm.nih.gov/34185076/

## Connected records

- cancers: [Astrocytoma, IDH-mutant (grades 2 to 4)](https://onco.cc/cancers/idh-mutant-astrocytoma/), [Central nervous system germ cell tumours (germinoma and non-germinomatous)](https://onco.cc/cancers/cns-germ-cell-tumours/), [Group 3 and group 4 medulloblastoma (non-WNT/non-SHH)](https://onco.cc/cancers/medulloblastoma-group-3-4/), [Meningioma](https://onco.cc/cancers/meningioma/), [Oligodendroglioma, IDH-mutant and 1p/19q-codeleted](https://onco.cc/cancers/oligodendroglioma/), [Paediatric high-grade glioma (excluding diffuse midline glioma)](https://onco.cc/cancers/paediatric-high-grade-glioma/), [SHH-activated medulloblastoma](https://onco.cc/cancers/medulloblastoma-shh/), [Spinal cord tumours (intramedullary and intradural)](https://onco.cc/cancers/spinal-cord-tumours/), [WNT-activated medulloblastoma](https://onco.cc/cancers/medulloblastoma-wnt/)
- journals: [Neuro-Oncology](https://onco.cc/journals/neuro-oncology/)

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