The WHO classification of tumours of the central nervous system is a World Health Organization Blue Book that defines, describes and classifies tumours of the central nervous system (CNS). Currently, as of 2023, clinicians are using the 5th edition, which incorporates recent advances in molecular pathology. The books lists ICD-O codes, CNS WHO grades and describes epidemiological, clinical, macroscopic and histopathological features, among others. The following is a simplified (deprecated) version of the fifth edition.

Types

1. Gliomas, glioneuronal tumors, and neuronal tumours

2. Choroid plexus tumours

3. Embryonal tumours

4. Pineal tumours

5. Cranial and paraspinal nerve tumours

6. Meningioma

7. Mesenchymal, non-meningothelial tumours

8. Melanocytic tumours

9. Hematolymphoid tumours

10. Germ cell tumours

11. Tumors of the sellar region

12. Metastases to the CNS

Terminology

The 5th WHO classification delineates distinct types of tumors, some of them being further divided into subtypes, rendering the former terms entity and variant obsolete. When molecular diagnostics are not complete enough to allow precise classification, diagnosis should be designated by appending not otherwise specified (NOS). In case of a full molecular workup which does not match any of the standard WHO diagnosis, tumors are to be labeled not elsewhere classified (NEC).

History

1979 WHO classification (1st edition)

1993 WHO classification (2nd edition)

Kleihues P, Burger PC, Scheithauer BW (eds) (1993) Histological typing of tumours of the central nervous system. World Health Organization international histological classification of tumours. Springer, Heidelberg

2000 WHO classification (3rd edition)

Kleihues P, Cavenee WK (eds) (2000) World Health Organization Classification of Tumours. Pathology and genetics of tumours of the nervous system. IARC Press

2007 WHO classification (4th edition)

This is the classification that began to suggest the use genetic information for classification.

2016 WHO classification (4th revised edition)

This was a substantial revision of the 4th edition. The reason it is not the 5th edition is that additions to the CNS volume were needed even though WHO was not up to 5th editions yet.

2021 WHO classification (5th edition)

The 5th edition incorporated many of the proposed changes outlined by the cIMPACT-NOW (the Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy - Not Official WHO).

WHO Classification of Tumours (Online Edition)

Since February 19, 2020, the WHO tumors classification has been accessible online as a subscription service, which includes the revised 4th edition.