The 2021 World Health Organization classification of gliomas: an imaging approach

The purpose of this pictorial essay is to describe the recommendations of the 2021 World Health Organization classification for adult-type and pediatric-type gliomas and to discuss the main modifications in relation to the previous (2016) classification, exemplified by imaging, histological, and molecular findings in nine patients followed at our institutions. In recent years, molecular biomarkers have gained importance in the diagnosis and classification of gliomas, mainly because they have been shown to correlate with the biological behavior and prognosis of such tumors. It is important for neuroradiologists to familiarize themselves with this new classification of central nervous system tumors, so that they can use this knowledge in evaluating and reporting the imaging examinations of patients with glioma.

Keywords:
Glioma/classification; Central nervous system neoplasms/classification; Glioblastoma/classification; Astrocytoma/classification

Authorship

Renata Tarraf Fernandes

Hospital de Câncer de Barretos, Barretos, SP, BrazilHospital de Câncer de BarretosBrazilBarretos, SP, BrazilHospital de Câncer de Barretos, Barretos, SP, Brazil

https://orcid.org/0000-0003-4823-9873

Gustavo Ramos Teixeira

Hospital de Câncer de Barretos, Barretos, SP, BrazilHospital de Câncer de BarretosBrazilBarretos, SP, BrazilHospital de Câncer de Barretos, Barretos, SP, Brazil

https://orcid.org/0000-0001-8363-3513

Esther Cecin Mamere

Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN, BrazilUniversidade Federal do Rio Grande do NorteBrazilNatal, RN, BrazilUniversidade Federal do Rio Grande do Norte (UFRN), Natal, RN, Brazil

https://orcid.org/0000-0001-8480-7773

Gabriela Alencar Bandeira

Instituto de Radiologia do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (InRad/HC-FMUSP), São Paulo, SP, BrazilUniversidade de São PauloBrazilSão Paulo, SP, BrazilInstituto de Radiologia do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (InRad/HC-FMUSP), São Paulo, SP, Brazil

https://orcid.org/0000-0002-9605-1915

Augusto Elias Mamere Correspondence: Dr. Augusto Elias Mamere. Hospital de Câncer de Barretos. Rua Antenor Duarte Vilela, 1331, Doutor Paulo Prata. Barretos, SP, Brazil, 14784-400. E-mail: mamere.augusto@gmail.com.

Hospital de Câncer de Barretos, Barretos, SP, BrazilHospital de Câncer de BarretosBrazilBarretos, SP, BrazilHospital de Câncer de Barretos, Barretos, SP, Brazil

https://orcid.org/0000-0001-9111-6700

Correspondence: Dr. Augusto Elias Mamere. Hospital de Câncer de Barretos. Rua Antenor Duarte Vilela, 1331, Doutor Paulo Prata. Barretos, SP, Brazil, 14784-400. E-mail: mamere.augusto@gmail.com.

SCIMAGO INSTITUTIONS RANKINGS

Hospital de Câncer de Barretos, Barretos, SP, BrazilHospital de Câncer de BarretosBrazilBarretos, SP, BrazilHospital de Câncer de Barretos, Barretos, SP, Brazil

Figures

Figures (10)

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Figure 1
MRI scans of a 25-year-old male patient. A T2-weighted sequence (A) and a FLAIR sequence (B), both acquired in 2010, showing an infiltrative lesion, with high signal intensity and a T2-FLAIR mismatch sign (arrows), in the left frontal lobe. After surgical resection, the patient received a diagnosis of IDH-mutant grade 2 astrocytoma. A follow-up examination in 2021 (11 years later) showed enlargement of the remaining lesion. At that time, a fat-saturated T1-weighted sequence (C) showed areas of intense contrast enhancement in the solid areas (arrow) and a dynamic T2* perfusion-weighted sequence (D) showed high rCBV (arrow on color map), both findings being consistent with transformation to high grade. After a second surgical resection, a diagnosis of IDH-mutant grade 4 astrocytoma was made. No 1p/19q codeletion was observed.

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Figure 2
A 26-year-old female patient. A computed tomography scan (A) and MRI scans (B,C), showing an infiltrative, poorly defined lesion, containing gross calcifications (arrow in A), in the right cerebral hemisphere. Gadolinium contrast-enhanced, fat-saturated T1-weighted sequence showing a small area of contrast enhancement within the lesion (arrow in B) and a dynamic T2* perfusion-weighted sequence (C) showing a high rCBV (arrow on color map). The results of the histological and molecular analyses were consistent with a diagnosis of IDH-mutant, 1p/19q-codeleted grade 2 oligodendroglioma.

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Figure 3
MRI scans of a 53-year-old male patient. A FLAIR sequence (A) showing an infiltrative lesion with high signal intensity in the right temporal lobe, together with an area of necrosis/liquefaction (arrow), and a gadolinium contrast-enhanced, fat-saturated T1-weighted sequence (B) showing a small focus of contrast enhancement (arrow), both findings being suggestive of a high-grade lesion. The histological findings were consistent with a diagnosis of low-grade (grade 2) astrocytoma. However, the molecular study showed IDH wild-type, mutation of the TERT promoter gene, and amplification of the EGFR gene, consistent with a diagnosis of molecularly defined glioblastoma, according to the latest (2021) WHO classification.

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Figure 4
MRI examination of a 20-year-old female patient diagnosed with a polymorphous low-grade neuroepithelial tumor of the young. A T2-weighted sequence showing a well-defined intra-axial temporal lesion on the left, with high signal intensity and containing small cystic areas, the slow growth of which led to remodeling of the cranial vault (arrow).

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Figure 5
MRI scans of a 16-year-old male patient. A FLAIR sequence (A) showing an infiltrative lesion in the left frontal lobe (arrow) and a T1-weighted sequence (B) showing areas of high signal intensity. The lesion showed slow growth, which resulted in remodeling of the adjacent cranial vault (arrow in B). The histological findings were consistent with a diagnosis of angiocentric glioma.

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Figure 6
MRI scans of a 9-year-old male patient diagnosed with H3K27-altered diffuse midline glioma. A T2-weighted sequence (A) showing an expansile, infiltrative lesion affecting the pons, with a heterogeneous appearance and cystic or necrotic areas (arrow). A gadolinium contrast-enhanced, fat-saturated T1-weighted sequence (B) showing heterogeneous contrast enhancement of the solid portions of the tumor (arrow). The histological findings were consistent with a diagnosis of high-grade glioma, and the molecular evaluation showed that the lesion was IDH wild-type and H3K27-mutated.

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Figure 7
MRI examination of a 12-year-old male patient diagnosed with H3K27-altered diffuse midline glioma. A T2-weighted sequence showing an intra-axial lesion, with high signal intensity, in the spinal cord (arrow). The results of the histological and molecular analyses were consistent with a diagnosis of IDH wild-type, H3K27-altered diffuse midline glioma.

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Figure 8
MRI scans of a 32-year-old female patient diagnosed with H3G34-mutant diffuse hemispheric glioma. A T2-weighted sequence (A) showing an expansile, heterogeneous lesion, with an isointense signal delineating central cystic/necrotic areas (arrow), in the right frontal lobe, and a diffusion-weighted sequence (B) showing low apparent diffusion coefficient values in its solid portions (arrow), indicative of restricted diffusion. The histological findings were consistent with a diagnosis of high-grade glioma, and the molecular evaluation showed that the lesion was IDH wild-type and H3G34-mutant.

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Figure 9
MRI scans of a 11-year-old male patient diagnosed with pediatric-type, H3 wild-type, IDH wild-type high-grade diffuse glioma. A T2-weighted sequence (A) showing an expansile, infiltrative lesion with high signal intensity, in the right temporal lobe (arrow) and a gadolinium contrast-enhanced, fat-saturated T1-weighted sequence (B) showing discrete, heterogeneous contrast enhancement delineating an area without central enhancement, consistent with necrosis (arrow). The histological findings were consistent with a diagnosis of high-grade glial neoplasia, and the molecular evaluation showed that the lesion was H3 wild-type and IDH wild-type, without TERT promoter amplification.

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Figure 10
MRI examination of a 11-month-old male patient diagnosed with pediatric-type hemispheric glioma. A gadolinium contrast-enhanced, fat-saturated T1-weighted sequence showing an expansile, heterogeneous lesion in the left frontal lobe, with cystic or necrotic areas and heterogeneous contrast enhancement (arrow). The histological findings were consistent with a diagnosis of high-grade glioma, and a molecular panel revealed neurotrophic tyrosine receptor kinase gene fusion.

Figure 1 MRI scans of a 25-year-old male patient. A T2-weighted sequence (A) and a FLAIR sequence (B), both acquired in 2010, showing an infiltrative lesion, with high signal intensity and a T2-FLAIR mismatch sign (arrows), in the left frontal lobe. After surgical resection, the patient received a diagnosis of IDH-mutant grade 2 astrocytoma. A follow-up examination in 2021 (11 years later) showed enlargement of the remaining lesion. At that time, a fat-saturated T1-weighted sequence (C) showed areas of intense contrast enhancement in the solid areas (arrow) and a dynamic T2* perfusion-weighted sequence (D) showed high rCBV (arrow on color map), both findings being consistent with transformation to high grade. After a second surgical resection, a diagnosis of IDH-mutant grade 4 astrocytoma was made. No 1p/19q codeletion was observed.

Figure 2 A 26-year-old female patient. A computed tomography scan (A) and MRI scans (B,C), showing an infiltrative, poorly defined lesion, containing gross calcifications (arrow in A), in the right cerebral hemisphere. Gadolinium contrast-enhanced, fat-saturated T1-weighted sequence showing a small area of contrast enhancement within the lesion (arrow in B) and a dynamic T2* perfusion-weighted sequence (C) showing a high rCBV (arrow on color map). The results of the histological and molecular analyses were consistent with a diagnosis of IDH-mutant, 1p/19q-codeleted grade 2 oligodendroglioma.

Figure 3 MRI scans of a 53-year-old male patient. A FLAIR sequence (A) showing an infiltrative lesion with high signal intensity in the right temporal lobe, together with an area of necrosis/liquefaction (arrow), and a gadolinium contrast-enhanced, fat-saturated T1-weighted sequence (B) showing a small focus of contrast enhancement (arrow), both findings being suggestive of a high-grade lesion. The histological findings were consistent with a diagnosis of low-grade (grade 2) astrocytoma. However, the molecular study showed IDH wild-type, mutation of the TERT promoter gene, and amplification of the EGFR gene, consistent with a diagnosis of molecularly defined glioblastoma, according to the latest (2021) WHO classification.

Figure 4 MRI examination of a 20-year-old female patient diagnosed with a polymorphous low-grade neuroepithelial tumor of the young. A T2-weighted sequence showing a well-defined intra-axial temporal lesion on the left, with high signal intensity and containing small cystic areas, the slow growth of which led to remodeling of the cranial vault (arrow).

Figure 5 MRI scans of a 16-year-old male patient. A FLAIR sequence (A) showing an infiltrative lesion in the left frontal lobe (arrow) and a T1-weighted sequence (B) showing areas of high signal intensity. The lesion showed slow growth, which resulted in remodeling of the adjacent cranial vault (arrow in B). The histological findings were consistent with a diagnosis of angiocentric glioma.

Figure 6 MRI scans of a 9-year-old male patient diagnosed with H3K27-altered diffuse midline glioma. A T2-weighted sequence (A) showing an expansile, infiltrative lesion affecting the pons, with a heterogeneous appearance and cystic or necrotic areas (arrow). A gadolinium contrast-enhanced, fat-saturated T1-weighted sequence (B) showing heterogeneous contrast enhancement of the solid portions of the tumor (arrow). The histological findings were consistent with a diagnosis of high-grade glioma, and the molecular evaluation showed that the lesion was IDH wild-type and H3K27-mutated.

Figure 7 MRI examination of a 12-year-old male patient diagnosed with H3K27-altered diffuse midline glioma. A T2-weighted sequence showing an intra-axial lesion, with high signal intensity, in the spinal cord (arrow). The results of the histological and molecular analyses were consistent with a diagnosis of IDH wild-type, H3K27-altered diffuse midline glioma.

Figure 8 MRI scans of a 32-year-old female patient diagnosed with H3G34-mutant diffuse hemispheric glioma. A T2-weighted sequence (A) showing an expansile, heterogeneous lesion, with an isointense signal delineating central cystic/necrotic areas (arrow), in the right frontal lobe, and a diffusion-weighted sequence (B) showing low apparent diffusion coefficient values in its solid portions (arrow), indicative of restricted diffusion. The histological findings were consistent with a diagnosis of high-grade glioma, and the molecular evaluation showed that the lesion was IDH wild-type and H3G34-mutant.

Figure 9 MRI scans of a 11-year-old male patient diagnosed with pediatric-type, H3 wild-type, IDH wild-type high-grade diffuse glioma. A T2-weighted sequence (A) showing an expansile, infiltrative lesion with high signal intensity, in the right temporal lobe (arrow) and a gadolinium contrast-enhanced, fat-saturated T1-weighted sequence (B) showing discrete, heterogeneous contrast enhancement delineating an area without central enhancement, consistent with necrosis (arrow). The histological findings were consistent with a diagnosis of high-grade glial neoplasia, and the molecular evaluation showed that the lesion was H3 wild-type and IDH wild-type, without TERT promoter amplification.

Figure 10 MRI examination of a 11-month-old male patient diagnosed with pediatric-type hemispheric glioma. A gadolinium contrast-enhanced, fat-saturated T1-weighted sequence showing an expansile, heterogeneous lesion in the left frontal lobe, with cystic or necrotic areas and heterogeneous contrast enhancement (arrow). The histological findings were consistent with a diagnosis of high-grade glioma, and a molecular panel revealed neurotrophic tyrosine receptor kinase gene fusion.

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The 2021 World Health Organization classification of gliomas: an imaging approach

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[1] Correspondence: Dr. Augusto Elias Mamere. Hospital de Câncer de Barretos. Rua Antenor Duarte Vilela, 1331, Doutor Paulo Prata. Barretos, SP, Brazil, 14784-400. E-mail: mamere.augusto@gmail.com.