CNS & pituitary tumors
Gliomas, glioneuronal tumors, and neuronal tumors
WHO grading of gliomas
Authors: Rebecca Yoda, M.D., P.J. Cimino, M.D., Ph.D.
Editorial Board Member: Meaghan Morris, M.D., Ph.D.
Deputy Editor-in-Chief: Chunyu Cai, M.D., Ph.D.
Last author update: 14 March 2022
Last staff update: 26 April 2023
Copyright: 2002-2024, PathologyOutlines.com, Inc.
PubMed Search: WHO grading of gliomas[TI] 2021 free full text[SB]
Table of Contents
Definition / general | Major updates | WHO (2021) | Diagrams / tables | Microscopic (histologic) images | Molecular / cytogenetics images | Videos | Additional references | Board review style question #1 | Board review style answer #1Cite this page: Yoda R, Cimino PJ. WHO grading of gliomas. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/cnstumorwhograding.html. Accessed April 25th, 2024.
Definition / general
- CNS WHO grading of gliomas according to the WHO Classification of Central Nervous System Tumors, 5th edition, published in 2021
Major updates
- Standardization with other fifth edition WHO classification systems (Neuro Oncol 2021;23:1231)
- Switch from Roman to Arabic numeral system
- The term "type" replaces "entity" and "subtype" replaces "variant"
- Shift toward within tumor type grading
- Removal of modifier terms, such as anaplastic
- IDH mutant astrocytic gliomas were 3 separate entities under the 2016 WHO (diffuse astrocytoma, anaplastic astrocytoma and glioblastoma) but now fall under the single tumor type astrocytoma, IDH mutant, with CNS WHO grade ranging from 2 to 4
- Oligodendroglioma, IDH mutant and 1p / 19q codeleted, is assigned a CNS WHO grade of 2 or 3
- Pleomorphic xanthroastrocytoma is assigned a CNS WHO grade of 2 or 3
- Terms that are no longer recommended include diffuse astrocytoma, anaplastic astrocytoma, glioblastoma IDH mutant, anaplastic oligodendroglioma and anaplastic pleomorphic xanthoastrocytoma
- To emphasize difference of grading between CNS and non-CNS tumors, the term CNS WHO grade is endorsed
- Allows designation of not otherwise specified (NOS) or not elsewhere classified (NEC) as modifiers
- Not otherwise specified (NOS): applied when there is lack of diagnostic information (histological or molecular) necessary to classify glioma as a specific WHO diagnostic entity
- Not elsewhere classified (NEC): applied when there is sufficient diagnostic information available (histological and molecular) but the results do not allow for the glioma to be classified as a specific WHO diagnostic entity - often ending up more as a descriptive diagnosis
- New tumor type groupings
- Adult type diffuse gliomas
- Pediatric type diffuse low grade gliomas
- Pediatric type diffuse high grade gliomas
- Circumscribed astrocytic gliomas
- New glioma types
- Diffuse astrocytoma, MYB or MYBL1 altered
- Polymorphous low grade neuroepithelial tumor of the young
- Diffuse low grade glioma, MAPK pathway altered
- Diffuse hemispheric glioma, H3 G34 mutant
- Diffuse pediatric type high grade glioma, H3 wildtype and IDH wildtype
- Infant type hemispheric glioma
- High grade astrocytoma with piloid features
- Removed glioma types
- Diffuse astrocytoma, IDH wildtype
- Anaplastic astrocytoma, IDH wildtype
- Renamed glioma types
- Astrocytoma, IDH mutant
- Eliminates the following previously used terms: diffuse astrocytoma, IDH mutant; anaplastic astrocytoma, IDH mutant; and glioblastoma, IDH mutant
- Diffuse midline glioma, H3 K27 altered
- Terminology replaces the term mutant with altered, to include other mechanisms of histone alteration (e.g., EZHIP overexpression)
- Chordoid glioma
- Omits "of the third ventricle" anatomical designation
- Astroblastoma, MN1 altered
- Adds molecular criterion for diagnosis
- Astrocytoma, IDH mutant
- Changes to existing grading criteria require that either histological or molecular features are present (adult type diffuse gliomas)
- IDH mutant astrocytoma, CNS WHO grade 4 (Neuro Oncol 2021;23:1231)
- IDH mutant diffuse astrocytic glioma with CDKN2A / CDKN2B homozygous deletion is assigned a CNS WHO grade 4, even in the absence of microvascular proliferation or necrosis
- Glioblastoma, IDH wildtype, CNS WHO grade 4 (Acta Neuropathol 2018;136:805)
- Changes require that either histological or molecular criteria are present in order to obtain diagnosis
- Requirements: a diffuse astrocytic glioma with any one or more of the following: microvascular proliferation, necrosis, TERT promoter mutation, EGFR amplification, gain of chromosome 7 with concomitant loss of chromosome 10
- IDH mutant astrocytoma, CNS WHO grade 4 (Neuro Oncol 2021;23:1231)
WHO (2021)
-
Adult type diffuse gliomas ICD-O codes
- Astrocytoma, IDH mutant
- Astrocytoma, IDH mutant, CNS WHO grade 2 9400/3
- Astrocytoma, IDH mutant, CNS WHO grade 3 9401/3
- Astrocytoma, IDH mutant, CNS WHO grade 4 9445/3
- Oligodendroglioma, IDH mutant and 1p / 19q codeleted
- Oligodendroglioma, IDH mutant and 1p / 19q codeleted, CNS WHO grade 2 9450/3
- Oligodendroglioma, IDH mutant and 1p / 19q codeleted, CNS WHO grade 3 9451/3
- Glioblastoma, IDH wildtype, CNS WHO grade 4 9440/3
-
Pediatric type diffuse low grade gliomas ICD-O codes
- Diffuse astrocytoma, MYB or MYBL1 altered, CNS WHO grade 1 9421/1
- Angiocentric glioma, CNS WHO grade 1 9431/1
- Polymorphous low grade neuroepithelial tumor of the young, CNS WHO grade 1 9413/0
- Diffuse low grade glioma, MAPK pathway altered* 9421/1
-
Pediatric type diffuse high grade gliomas ICD-O codes
- Diffuse midline glioma, H3 K27 altered, CNS WHO grade 4 9385/3
- Diffuse hemispheric glioma, H3 G34 mutant, CNS WHO grade 4 9385/3
- Diffuse pediatric type high grade glioma, H3 wildtype and IDH wildtype, CNS WHO grade 4 9385/3
- Infant type hemispheric glioma* 9385/3
-
Circumscribed astrocytic gliomas ICD-O codes
- Pilocytic astrocytoma, CNS WHO grade 1 9421/1
- High grade astrocytoma with piloid features* 9421/3
- Pleomorphic xanthoastrocytoma, CNS WHO grade 2 or 3 9424/3
- Subependymal giant cell astrocytoma, CNS WHO grade 1 9384/1
- Chordoid glioma, CNS WHO grade 2 9444/1
- Astroblastoma, MN1 altered* 9430/3
- *Definitive CNS WHO grade not established
Diagrams / tables
Contributed by P.J. Cimino, M.D., Ph.D.
Adult type IDH mutant gliomas
Adult type IDH wildtype gliomas
Microscopic (histologic) images
Contributed by P.J. Cimino, M.D., Ph.D.
Astrocytoma lacking mitoses
Increased mitotic activity
Pseudopalisading necrosis
Microvascular proliferation
Molecular / cytogenetics images
Contributed by P.J. Cimino, M.D., Ph.D.
Glioblastoma EGFR amplification
Glioblastoma copy number plot
Images hosted on other servers:
Glioblastoma TERT promoter mutation
Videos
2021 WHO classification of CNS tumors: update I - gliomas
Additional references
Board review style question #1
This IDH mutant astrocytoma is from a 40 year old woman. There is no microvascular proliferation or necrosis identified. According to the 5th edition of the WHO classification of CNS tumors (2021), a CNS WHO grade 4 should be applied if which of the following genetic alterations is present?
- ATRX loss
- CDKN2A homozygous deletion
- Chromosome 1p / 19q codeletion
- EGFR amplification
- TERT promoter mutation
Board review style answer #1
B. CDKN2A homozygous deletion. The presence of CDKN2A or CDKN2B homozygous deletion in an astrocytoma, IDH mutant, necessitates a CNS WHO grade of 4, even in the absence of histologic features (i.e., lacking microvascular proliferation and spontaneous necrosis).
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Reference: WHO grading of gliomas
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Reference: WHO grading of gliomas
