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This document, published in Acta Neuropathologica Communications, discusses the identification of a subtype of diffuse midline glioma (DMG) called H3K27/MAPKinase co-altered. The study analyzes a cohort of 182 pediatric and adult cases of DMG, H3K27-altered and identifies 30 tumors with a loss of ATRX expression. The authors provide clinical, histopathological, and molecular data on these tumors and suggest that the loss of ATRX expression may be a potential diagnostic tool for identifying DMG, H3K27/MAPK co-altered. The study highlights the distinct features of this subtype and emphasizes the importance of integrating clinical, radiological, histopathological, and molecular results for an accurate diagnosis. [Extracted from the article]

Aims: The SOX10 transcription factor is important for the maturation of oligodendrocytes involved in central nervous system (CNS) myelination. Currently, very little information exists about its expression and potential use in CNS tumour diagnoses. The aim of our study was to characterize the expression of SOX10 in a large cohort of CNS tumours and to evaluate its potential use as a biomarker. Methods: We performed immunohistochemistry (IHC) for SOX10 and OLIG2 in a series of 683 cases of adult‐ and paediatric‐type CNS tumours from different subtypes. The nuclear immunostaining results for SOX10 and OLIG2 were scored as positive (≥10% positive tumour cells) or negative. Results: OLIG2 and SOX10 were positive in diffuse midline gliomas (DMG), H3‐mutant, and EZHIP‐overexpressed. However, in all DMG, EGFR‐mutant, SOX10 was constantly negative. In diffuse paediatric‐type high‐grade gliomas (HGG), all RTK1 cases were positive for both OLIG2 and SOX10. RTK2 cases were all negative for both OLIG2 and SOX10. MYCN cases variably expressed OLIG2 and were all immunonegative for SOX10. In glioblastoma, IDH‐wildtype, OLIG2 was mostly positive, but SOX10 was variably expressed, depending on the epigenetic subtype. All circumscribed astrocytic gliomas were positive for both OLIG2 and SOX10 except pleomorphic xanthoastrocytomas, astroblastomas, MN1‐altered, and subependymal giant cell astrocytomas. SOX10 was negative in ependymomas, meningiomas, pinealoblastomas, choroid plexus tumours, intracranial Ewing sarcomas, and embryonal tumours except neuroblastoma, FOXR2‐activated. Conclusion: To conclude, SOX10 can be incorporated into the IHC panel routinely used by neuropathologists in the diagnostic algorithm of embryonal tumours and for the subtyping of paediatric and adult‐type HGG. [ABSTRACT FROM AUTHOR]

This article discusses a case study of a rare brain tumor called diffuse midline glioma (DMG) with ependymal features. DMG is a type of brain tumor that primarily affects children and is characterized by alterations in a specific gene called H3K27. The case study focuses on a specific subtype of DMG called EGFR-subtype, which is associated with mutations in the EGFR gene. The study highlights the challenges in diagnosing this subtype and emphasizes the importance of integrating radiological, histopathological, genetic, and epigenetic data for an accurate diagnosis. The authors suggest that DMG with ependymal features may be misdiagnosed as another type of brain tumor called posterior fossa ependymoma, and further research is needed to better understand the characteristics and prognosis of this subtype. [Extracted from the article]

Therefore, histopathology (including p53 overexpression correlated to I TP53 i mutation), and FISH I MYCN/ID2 i may help diagnose pHGG-MYCN, using a simple algorithm approach (Fig. Interestingly, our results seem to show that pHGG-MYCN I MYCN+/ID2 + i are not associated with I TP53 i germline mutations, whereas Li-Fraumeni syndrome is present in the subgroup of I MYCN+/ID2- i . [Extracted from the article]

The authors report a rare case of most likely radiation-induced glioma (RIG) with epithelioid features and the presence of molecular features consistent with RIG. This occurred 70 years after craniofacial brachytherapy. Such a late development of radiation-induced glioblastoma (RIGBM) and the advanced age of presentation for an epithelioid glioblastoma are both unique in the literature. Despite not receiving the full course of adjuvant chemotherapy after surgery and radiotherapy, the patient displayed no signs of recurrence during a 5-year follow-up. RIGBM should be further studied to reveal potential unique clinical and molecular characteristics, as well as to better predict survival and treatment response. [ABSTRACT FROM AUTHOR]

Recent epigenomic analyses have revealed the existence of a new DNA methylation class (MC) of infant‐type hemispheric glioma (IHG). Like desmoplastic infantile ganglioglioma/astrocytoma (DIG/DIA), these tumors mainly affect infants and are supratentorial. While DIG/DIA is characterized by BRAF or RAF1 alterations, IHG has been shown to have receptor tyrosine kinase (RTK) gene fusions (ALK, ROS1, NTRK1/2/3, and MET). However, in this rapidly evolving field, a more comprehensive analysis of infantile glial/glioneuronal tumors including clinical, radiological, histopathological, and molecular data is needed. Here, we retrospectively investigated data from 30 infantile glial/glioneuronal tumors, consecutively compiled from our center. They were analyzed by two experienced pediatric neuroradiologists in consensus, without former knowledge of the molecular data. We also performed a comprehensive clinical, and histopathological examination (including molecular evaluation by next‐generation sequencing, RNA sequencing, and fluorescence in situ hybridization [FISH] analyses), as well as DNA methylation profiling for the samples having sufficient material available. The integrative histopathological, genetic, and epigenetic analyses, including t‐distributed stochastic neighbor embedding (t‐SNE) analyses segregated tumors into 10 DIG/DIA (33.3%), six IHG (20.0%), three gangliogliomas (10.0%), two pleomorphic xanthoastrocytomas (6.7%), two pilocytic astrocytomas (6.7%), two supratentorial ependymomas, ZFTA fusion‐positive (6.7%), two supratentorial ependymomas, YAP1 fusion‐positive (6.7%), two embryonal tumors with PLAGL2‐family amplification (6.7%), and one diffuse low‐grade glioma, MAPK‐pathway altered. This study highlights the significant differential features, in terms of histopathology (leptomeningeal infiltration, intense desmoplasia and ganglion cells in DIG/DIA and necrosis, microvascular proliferation, and siderophages in IHG), and radiology between DIG/DIA and IHG. Moreover, these results are consistent with the literature data concerning the molecular dichotomy (BRAF/RAF1 alterations vs. RTK genes' fusions) between DIG/DIA and IHG. This study characterized histopathologically and radiologically two additional cases of the novel embryonal tumor characterized by PLAGL2 gene amplification. [ABSTRACT FROM AUTHOR]

Background: Gliomas with FGFR3::TACC3 fusion mainly occur in adults, display pathological features of glioblastomas (GB) and are usually classified as glioblastoma, IDH-wildtype. However, cases demonstrating pathological features of low-grade glioma (LGG) lead to difficulties in classification and clinical management. We report a series of 8 GB and 14 LGG with FGFR3:TACC3 fusion in order to better characterize them. Methods: Centralized pathological examination, search for TERT promoter mutation and DNA-methylation profiling were performed in all cases. Search for prognostic factors was done by the Kaplan–Meir method. Results: TERT promoter mutation was recorded in all GB and 6/14 LGG. Among the 7 cases with a methylation score > 0.9 in the classifier (v12.5), 2 were classified as glioblastoma, 4 as ganglioglioma (GG) and 1 as dysembryoplastic neuroepithelial tumor (DNET). t-SNE analysis showed that the 22 cases clustered into three groups: one included 12 cases close to glioblastoma, IDH-wildtype methylation class (MC), 5 cases each clustered with GG or DNET MC but none with PLNTY MC. Unsupervised clustering analysis revealed four groups, two of them being clearly distinct: 5 cases shared age (< 40), pathological features of LGG, lack of TERT promoter mutation, FGFR3(Exon 17)::TACC3(Exon 10) fusion type and LGG MC. In contrast, 4 cases shared age (> 40), pathological features of glioblastoma, and were TERT-mutated. Relevant factors associated with a better prognosis were age < 40 and lack of TERT promoter mutation. Conclusion: Among gliomas with FGFR3::TACC3 fusion, age, TERT promoter mutation, pathological features, DNA-methylation profiling and fusion subtype are of interest to determine patients' risk. [ABSTRACT FROM AUTHOR]

Léa Guerrini-Rousseau and Arnault Tauziède-Espariat have contributed equally to this work In the current World Health Organization (WHO) Classification of Tumors of the Central Nervous System (CNS), pediatric high-grade gliomas (HGGs), I IDH- i and histone H3 I - i wildtype (WT) are divided into three molecular subtypes: RTK1, RTK2 and MYCN [[2]]. LFS cases do not seem to form a distinct subcluster in the DNA-methylation based classification of CNS tumors compared to those without a I TP53 i germline mutation. [Extracted from the article]

Aims: Dysembryoplastic neuroepithelial tumour (DNT) is a glioneuronal tumour that is challenging to diagnose, with a wide spectrum of histological features. Three histopathological patterns have been described: specific DNTs (both the simple form and the complex form) comprising the specific glioneuronal element, and also the non‐specific/diffuse form which lacks it, and has unclear phenotype–genotype correlations with numerous differential diagnoses. Methods: We used targeted methods (immunohistochemistry, fluorescence in situ hybridisation and targeted sequencing) and large‐scale genomic methodologies including DNA methylation profiling to perform an integrative analysis to better characterise a large retrospective cohort of 82 DNTs, enriched for tumours that showed progression on imaging. Results: We confirmed that specific DNTs are characterised by a single driver event with a high frequency of FGFR1 variants. However, a subset of DNA methylation‐confirmed DNTs harbour alternative genomic alterations to FGFR1 duplication/mutation. We also demonstrated that a subset of DNTs sharing the same FGFR1 alterations can show in situ progression. In contrast to the specific forms, "non‐specific/diffuse DNTs" corresponded to a heterogeneous molecular group encompassing diverse, newly‐described, molecularly distinct entities. Conclusions: Specific DNT is a homogeneous group of tumours sharing characteristics of paediatric low‐grade gliomas: a quiet genome with a recurrent genomic alteration in the RAS‐MAPK signalling pathway, a distinct DNA methylation profile and a good prognosis but showing progression in some cases. The "non‐specific/diffuse DNTs" subgroup encompasses various recently described histomolecular entities, such as PLNTY and diffuse astrocytoma, MYB or MYBL1 altered. [ABSTRACT FROM AUTHOR]

1:CAS:528:DC%2BC1cXpsV2hu7k%3D. 10.1007/s00401-018-1865-4 6 Navarro RE, Golub D, Hill T, McQuinn MW, William C, Zagzag D. Pediatric midline H3K27M-mutant tumor with disseminated leptomeningeal disease and glioneuronal features: case report and literature review. Gliomas with concomitant mutations of H3K27M and I BRAF/FGFR1 i are supposed to be associated with a better prognosis than other DMG, H3K27-altered according to some publications [[7]]. Arguing for this hypothesis, a previously published monothalamic tumor classified as ganglioglioma, H3K27M- and I BRAF i V600E-mutant presented secondary leptomeningeal dissemination 7 years after the initial diagnosis [[10]]. [Extracted from the article]

2 Molecular and clinical portrait of H3 wild-type DMG patients. a Clinicopathological and molecular annotations are provided as bars for 19 histone H3 wild-type DMG patients. Samples are arranged in columns with genes labeled along rows. b Distribution of normalized EZHIP gene expression level, in H3-K27M (green, n = 20) and H3 wild-type (grey, n = 11) DMG patients. We propose that these EZHIP/H3-WT tumors need to be considered similar to canonical DIPG/DMG, thus extending the spectrum of DMG with PRC2 inhibition beyond H3-K27M mutation. [Extracted from the article]

The "isomorphic subtype of diffuse astrocytoma" was identified histologically in 2004 as a supratentorial, highly differentiated glioma with low cellularity, low proliferation and focal diffuse brain infiltration. Patients typically had seizures since childhood and all were operated on as adults. To define the position of these lesions among brain tumours, we histologically, molecularly and clinically analysed 26 histologically prototypical isomorphic diffuse gliomas. Immunohistochemically, they were GFAP-positive, MAP2-, OLIG2- and CD34-negative, nuclear ATRX-expression was retained and proliferation was low. All 24 cases sequenced were IDH-wildtype. In cluster analyses of DNA methylation data, isomorphic diffuse gliomas formed a group clearly distinct from other glial/glio-neuronal brain tumours and normal hemispheric tissue, most closely related to paediatric MYB/MYBL1-altered diffuse astrocytomas and angiocentric gliomas. Half of the isomorphic diffuse gliomas had copy number alterations of MYBL1 or MYB (13/25, 52%). Gene fusions of MYBL1 or MYB with various gene partners were identified in 11/22 (50%) and were associated with an increased RNA-expression of the respective MYB-family gene. Integrating copy number alterations and available RNA sequencing data, 20/26 (77%) of isomorphic diffuse gliomas demonstrated MYBL1 (54%) or MYB (23%) alterations. Clinically, 89% of patients were seizure-free after surgery and all had a good outcome. In summary, we here define a distinct benign tumour class belonging to the family of MYB/MYBL1-altered gliomas. Isomorphic diffuse glioma occurs both in children and adults, has a concise morphology, frequent MYBL1 and MYB alterations and a specific DNA methylation profile. As an exclusively histological diagnosis may be very challenging and as paediatric MYB/MYBL1-altered diffuse astrocytomas may have the same gene fusions, we consider DNA methylation profiling very helpful for their identification. [ABSTRACT FROM AUTHOR]

Simple Summary: Despite progress in the biology and upfront treatment of childhood medulloblastoma, relapse is almost universally fatal. No standardized treatment has so far been established for these patients. By determining which characteristics are prognostic after relapse, treatment strategies may be optimized for each of these children. We demonstrated that molecular subgroup at diagnosis is a relevant prognostic factor of outcome after relapse. Moreover, we showed that time to relapse and the use of salvage radiotherapy at relapse might have a potential impact on post-relapse survival. Our data suggest that ongoing efforts toward a better understanding of the biology, timing and type of relapse would be important to understand the determinants of tumor behavior at relapse. This could help us address more specific questions on the best surveillance strategies after completion of the treatment and the introduction of risk-stratified second-line treatment strategies. Given the very poor prognosis for children with recurrent medulloblastoma, we aimed to identify prognostic factors for survival post-relapse in children with childhood medulloblastoma. We retrospectively collected clinico-biological data at diagnosis and main clinical characteristics at relapse of children newly diagnosed with a medulloblastoma between 2007 and 2017 at Gustave Roussy and Necker Hospital. At a median follow-up of 6.6 years (range, 0.4–12.3 years), relapse occurred in 48 out 155 patients (31%). The median time from diagnosis to relapse was 14.3 months (range, 1.2–87.2 months). Relapse was local in 9, metastatic in 22 and combined (local and metastatic) in 17 patients. Second-line treatment consisted of chemotherapy in 31 cases, radiotherapy in 9, SHH-inhibitor in four and no treatment in the remaining four. The 1-year overall survival rate post-relapse was 44.8% (CI 95%, 31.5% to 59.0%). While molecular subgrouping at diagnosis was significantly associated with survival post-relapse, the use of radiotherapy at relapse and time to first relapse (>12 months) might also have a potential impact on post-relapse survival. [ABSTRACT FROM AUTHOR]

Background: Children with constitutional mismatch repair deficiency (CMMRD) syndrome have an increased risk of high-grade gliomas (HGG), and brain imaging abnormalities. This study analyzes brain imaging features in CMMRD syndrome children versus those with HGG without CMMRD.Retrospective comparative analysis of brain imaging in 30 CMMRD children (20 boys, median age eight years, 22 with HGG), seven with Lynch syndrome (7 HGG), 39 with type 1 neurofibromatosis (NF1) (four with HGG) and 50 with HGG without MMR or NF1 pathogenic variant (“no-predisposition” patients).HGG in CMMRD and Lynch patients were predominantly hemispheric (versus midline) compared to NF1 and no-predisposition patients (91% and 86%, vs 25% and 54%, p = 0.004). CMMRD-associated tumors often had ill-defined boundaries (p = 0.008). All CMMRD patients exhibited at least one developmental venous anomaly (DVA), versus 14%, 10%, and 6% of Lynch, NF1, and no-predisposition patients (p < 0.0001). Multiple DVAs were observed in 83% of CMMRD patients, one NF1 patient (3%), and never in other groups (p < 0.0001). Cavernomas were discovered in 21% of CMMRD patients, never in other groups (p = 0.01). NF1-like focal areas of high T2-FLAIR signal intensity (FASI) were more prevalent in CMMRD patients than in Lynch or no-predisposition patients (50%, vs 20% and 0%, respectively, p < 0.0001). Subcortical and ill-limited FASI, possibly involving the cortex, were specific to CMMRD (p < 0.0001) and did not evolve in 93% of patients (13/14).Diffuse hemispherically located HGG associated with multiple DVAs, cavernomas, and NF1-like or subcortical FASI strongly suggests CMMRD syndrome compared to children with HGG in other contexts.The radiologic suggestion of CMMRD syndrome when confronted with HGGs in children may prompt genetic testing. This can influence therapeutic plans. Therefore, imaging features could potentially be incorporated into CMMRD testing recommendations.Using imaging to detect CMMRD syndrome early may improve patient care.CMMRD features include: hemispheric HGG with multiple developmental venous anomalies and NF1-like or subcortical areas with high T2-FLAIR intensity.We propose novel imaging features to improve the identification of potential CMMRD patients.Using imaging to detect CMMRD syndrome early may improve patient care.CMMRD features include: hemispheric HGG with multiple developmental venous anomalies and NF1-like or subcortical areas with high T2-FLAIR intensity.We propose novel imaging features to improve the identification of potential CMMRD patients.Methods: Children with constitutional mismatch repair deficiency (CMMRD) syndrome have an increased risk of high-grade gliomas (HGG), and brain imaging abnormalities. This study analyzes brain imaging features in CMMRD syndrome children versus those with HGG without CMMRD.Retrospective comparative analysis of brain imaging in 30 CMMRD children (20 boys, median age eight years, 22 with HGG), seven with Lynch syndrome (7 HGG), 39 with type 1 neurofibromatosis (NF1) (four with HGG) and 50 with HGG without MMR or NF1 pathogenic variant (“no-predisposition” patients).HGG in CMMRD and Lynch patients were predominantly hemispheric (versus midline) compared to NF1 and no-predisposition patients (91% and 86%, vs 25% and 54%, p = 0.004). CMMRD-associated tumors often had ill-defined boundaries (p = 0.008). All CMMRD patients exhibited at least one developmental venous anomaly (DVA), versus 14%, 10%, and 6% of Lynch, NF1, and no-predisposition patients (p < 0.0001). Multiple DVAs were observed in 83% of CMMRD patients, one NF1 patient (3%), and never in other groups (p < 0.0001). Cavernomas were discovered in 21% of CMMRD patients, never in other groups (p = 0.01). NF1-like focal areas of high T2-FLAIR signal intensity (FASI) were more prevalent in CMMRD patients than in Lynch or no-predisposition patients (50%, vs 20% and 0%, respectively, p < 0.0001). Subcortical and ill-limited FASI, possibly involving the cortex, were specific to CMMRD (p < 0.0001) and did not evolve in 93% of patients (13/14).Diffuse hemispherically located HGG associated with multiple DVAs, cavernomas, and NF1-like or subcortical FASI strongly suggests CMMRD syndrome compared to children with HGG in other contexts.The radiologic suggestion of CMMRD syndrome when confronted with HGGs in children may prompt genetic testing. This can influence therapeutic plans. Therefore, imaging features could potentially be incorporated into CMMRD testing recommendations.Using imaging to detect CMMRD syndrome early may improve patient care.CMMRD features include: hemispheric HGG with multiple developmental venous anomalies and NF1-like or subcortical areas with high T2-FLAIR intensity.We propose novel imaging features to improve the identification of potential CMMRD patients.Using imaging to detect CMMRD syndrome early may improve patient care.CMMRD features include: hemispheric HGG with multiple developmental venous anomalies and NF1-like or subcortical areas with high T2-FLAIR intensity.We propose novel imaging features to improve the identification of potential CMMRD patients.Results: Children with constitutional mismatch repair deficiency (CMMRD) syndrome have an increased risk of high-grade gliomas (HGG), and brain imaging abnormalities. This study analyzes brain imaging features in CMMRD syndrome children versus those with HGG without CMMRD.Retrospective comparative analysis of brain imaging in 30 CMMRD children (20 boys, median age eight years, 22 with HGG), seven with Lynch syndrome (7 HGG), 39 with type 1 neurofibromatosis (NF1) (four with HGG) and 50 with HGG without MMR or NF1 pathogenic variant (“no-predisposition” patients).HGG in CMMRD and Lynch patients were predominantly hemispheric (versus midline) compared to NF1 and no-predisposition patients (91% and 86%, vs 25% and 54%, p = 0.004). CMMRD-associated tumors often had ill-defined boundaries (p = 0.008). All CMMRD patients exhibited at least one developmental venous anomaly (DVA), versus 14%, 10%, and 6% of Lynch, NF1, and no-predisposition patients (p < 0.0001). Multiple DVAs were observed in 83% of CMMRD patients, one NF1 patient (3%), and never in other groups (p < 0.0001). Cavernomas were discovered in 21% of CMMRD patients, never in other groups (p = 0.01). NF1-like focal areas of high T2-FLAIR signal intensity (FASI) were more prevalent in CMMRD patients than in Lynch or no-predisposition patients (50%, vs 20% and 0%, respectively, p < 0.0001). Subcortical and ill-limited FASI, possibly involving the cortex, were specific to CMMRD (p < 0.0001) and did not evolve in 93% of patients (13/14).Diffuse hemispherically located HGG associated with multiple DVAs, cavernomas, and NF1-like or subcortical FASI strongly suggests CMMRD syndrome compared to children with HGG in other contexts.The radiologic suggestion of CMMRD syndrome when confronted with HGGs in children may prompt genetic testing. This can influence therapeutic plans. Therefore, imaging features could potentially be incorporated into CMMRD testing recommendations.Using imaging to detect CMMRD syndrome early may improve patient care.CMMRD features include: hemispheric HGG with multiple developmental venous anomalies and NF1-like or subcortical areas with high T2-FLAIR intensity.We propose novel imaging features to improve the identification of potential CMMRD patients.Using imaging to detect CMMRD syndrome early may improve patient care.CMMRD features include: hemispheric HGG with multiple developmental venous anomalies and NF1-like or subcortical areas with high T2-FLAIR intensity.We propose novel imaging features to improve the identification of potential CMMRD patients.Conclusion: Children with constitutional mismatch repair deficiency (CMMRD) syndrome have an increased risk of high-grade gliomas (HGG), and brain imaging abnormalities. This study analyzes brain imaging features in CMMRD syndrome children versus those with HGG without CMMRD.Retrospective comparative analysis of brain imaging in 30 CMMRD children (20 boys, median age eight years, 22 with HGG), seven with Lynch syndrome (7 HGG), 39 with type 1 neurofibromatosis (NF1) (four with HGG) and 50 with HGG without MMR or NF1 pathogenic variant (“no-predisposition” patients).HGG in CMMRD and Lynch patients were predominantly hemispheric (versus midline) compared to NF1 and no-predisposition patients (91% and 86%, vs 25% and 54%, p = 0.004). CMMRD-associated tumors often had ill-defined boundaries (p = 0.008). All CMMRD patients exhibited at least one developmental venous anomaly (DVA), versus 14%, 10%, and 6% of Lynch, NF1, and no-predisposition patients (p < 0.0001). Multiple DVAs were observed in 83% of CMMRD patients, one NF1 patient (3%), and never in other groups (p < 0.0001). Cavernomas were discovered in 21% of CMMRD patients, never in other groups (p = 0.01). NF1-like focal areas of high T2-FLAIR signal intensity (FASI) were more prevalent in CMMRD patients than in Lynch or no-predisposition patients (50%, vs 20% and 0%, respectively, p < 0.0001). Subcortical and ill-limited FASI, possibly involving the cortex, were specific to CMMRD (p < 0.0001) and did not evolve in 93% of patients (13/14).Diffuse hemispherically located HGG associated with multiple DVAs, cavernomas, and NF1-like or subcortical FASI strongly suggests CMMRD syndrome compared to children with HGG in other contexts.The radiologic suggestion of CMMRD syndrome when confronted with HGGs in children may prompt genetic testing. This can influence therapeutic plans. Therefore, imaging features could potentially be incorporated into CMMRD testing recommendations.Using imaging to detect CMMRD syndrome early may improve patient care.CMMRD features include: hemispheric HGG with multiple developmental venous anomalies and NF1-like or subcortical areas with high T2-FLAIR intensity.We propose novel imaging features to improve the identification of potential CMMRD patients.Using imaging to detect CMMRD syndrome early may improve patient care.CMMRD features include: hemispheric HGG with multiple developmental venous anomalies and NF1-like or subcortical areas with high T2-FLAIR intensity.We propose novel imaging features to improve the identification of potential CMMRD patients.Clinical relevance statement: Children with constitutional mismatch repair deficiency (CMMRD) syndrome have an increased risk of high-grade gliomas (HGG), and brain imaging abnormalities. This study analyzes brain imaging features in CMMRD syndrome children versus those with HGG without CMMRD.Retrospective comparative analysis of brain imaging in 30 CMMRD children (20 boys, median age eight years, 22 with HGG), seven with Lynch syndrome (7 HGG), 39 with type 1 neurofibromatosis (NF1) (four with HGG) and 50 with HGG without MMR or NF1 pathogenic variant (“no-predisposition” patients).HGG in CMMRD and Lynch patients were predominantly hemispheric (versus midline) compared to NF1 and no-predisposition patients (91% and 86%, vs 25% and 54%, p = 0.004). CMMRD-associated tumors often had ill-defined boundaries (p = 0.008). All CMMRD patients exhibited at least one developmental venous anomaly (DVA), versus 14%, 10%, and 6% of Lynch, NF1, and no-predisposition patients (p < 0.0001). Multiple DVAs were observed in 83% of CMMRD patients, one NF1 patient (3%), and never in other groups (p < 0.0001). Cavernomas were discovered in 21% of CMMRD patients, never in other groups (p = 0.01). NF1-like focal areas of high T2-FLAIR signal intensity (FASI) were more prevalent in CMMRD patients than in Lynch or no-predisposition patients (50%, vs 20% and 0%, respectively, p < 0.0001). Subcortical and ill-limited FASI, possibly involving the cortex, were specific to CMMRD (p < 0.0001) and did not evolve in 93% of patients (13/14).Diffuse hemispherically located HGG associated with multiple DVAs, cavernomas, and NF1-like or subcortical FASI strongly suggests CMMRD syndrome compared to children with HGG in other contexts.The radiologic suggestion of CMMRD syndrome when confronted with HGGs in children may prompt genetic testing. This can influence therapeutic plans. Therefore, imaging features could potentially be incorporated into CMMRD testing recommendations.Using imaging to detect CMMRD syndrome early may improve patient care.CMMRD features include: hemispheric HGG with multiple developmental venous anomalies and NF1-like or subcortical areas with high T2-FLAIR intensity.We propose novel imaging features to improve the identification of potential CMMRD patients.Using imaging to detect CMMRD syndrome early may improve patient care.CMMRD features include: hemispheric HGG with multiple developmental venous anomalies and NF1-like or subcortical areas with high T2-FLAIR intensity.We propose novel imaging features to improve the identification of potential CMMRD patients.Key Points: Children with constitutional mismatch repair deficiency (CMMRD) syndrome have an increased risk of high-grade gliomas (HGG), and brain imaging abnormalities. This study analyzes brain imaging features in CMMRD syndrome children versus those with HGG without CMMRD.Retrospective comparative analysis of brain imaging in 30 CMMRD children (20 boys, median age eight years, 22 with HGG), seven with Lynch syndrome (7 HGG), 39 with type 1 neurofibromatosis (NF1) (four with HGG) and 50 with HGG without MMR or NF1 pathogenic variant (“no-predisposition” patients).HGG in CMMRD and Lynch patients were predominantly hemispheric (versus midline) compared to NF1 and no-predisposition patients (91% and 86%, vs 25% and 54%, p = 0.004). CMMRD-associated tumors often had ill-defined boundaries (p = 0.008). All CMMRD patients exhibited at least one developmental venous anomaly (DVA), versus 14%, 10%, and 6% of Lynch, NF1, and no-predisposition patients (p < 0.0001). Multiple DVAs were observed in 83% of CMMRD patients, one NF1 patient (3%), and never in other groups (p < 0.0001). Cavernomas were discovered in 21% of CMMRD patients, never in other groups (p = 0.01). NF1-like focal areas of high T2-FLAIR signal intensity (FASI) were more prevalent in CMMRD patients than in Lynch or no-predisposition patients (50%, vs 20% and 0%, respectively, p < 0.0001). Subcortical and ill-limited FASI, possibly involving the cortex, were specific to CMMRD (p < 0.0001) and did not evolve in 93% of patients (13/14).Diffuse hemispherically located HGG associated with multiple DVAs, cavernomas, and NF1-like or subcortical FASI strongly suggests CMMRD syndrome compared to children with HGG in other contexts.The radiologic suggestion of CMMRD syndrome when confronted with HGGs in children may prompt genetic testing. This can influence therapeutic plans. Therefore, imaging features could potentially be incorporated into CMMRD testing recommendations.Using imaging to detect CMMRD syndrome early may improve patient care.CMMRD features include: hemispheric HGG with multiple developmental venous anomalies and NF1-like or subcortical areas with high T2-FLAIR intensity.We propose novel imaging features to improve the identification of potential CMMRD patients.Using imaging to detect CMMRD syndrome early may improve patient care.CMMRD features include: hemispheric HGG with multiple developmental venous anomalies and NF1-like or subcortical areas with high T2-FLAIR intensity.We propose novel imaging features to improve the identification of potential CMMRD patients.Graphical Abstract: Children with constitutional mismatch repair deficiency (CMMRD) syndrome have an increased risk of high-grade gliomas (HGG), and brain imaging abnormalities. This study analyzes brain imaging features in CMMRD syndrome children versus those with HGG without CMMRD.Retrospective comparative analysis of brain imaging in 30 CMMRD children (20 boys, median age eight years, 22 with HGG), seven with Lynch syndrome (7 HGG), 39 with type 1 neurofibromatosis (NF1) (four with HGG) and 50 with HGG without MMR or NF1 pathogenic variant (“no-predisposition” patients).HGG in CMMRD and Lynch patients were predominantly hemispheric (versus midline) compared to NF1 and no-predisposition patients (91% and 86%, vs 25% and 54%, p = 0.004). CMMRD-associated tumors often had ill-defined boundaries (p = 0.008). All CMMRD patients exhibited at least one developmental venous anomaly (DVA), versus 14%, 10%, and 6% of Lynch, NF1, and no-predisposition patients (p < 0.0001). Multiple DVAs were observed in 83% of CMMRD patients, one NF1 patient (3%), and never in other groups (p < 0.0001). Cavernomas were discovered in 21% of CMMRD patients, never in other groups (p = 0.01). NF1-like focal areas of high T2-FLAIR signal intensity (FASI) were more prevalent in CMMRD patients than in Lynch or no-predisposition patients (50%, vs 20% and 0%, respectively, p < 0.0001). Subcortical and ill-limited FASI, possibly involving the cortex, were specific to CMMRD (p < 0.0001) and did not evolve in 93% of patients (13/14).Diffuse hemispherically located HGG associated with multiple DVAs, cavernomas, and NF1-like or subcortical FASI strongly suggests CMMRD syndrome compared to children with HGG in other contexts.The radiologic suggestion of CMMRD syndrome when confronted with HGGs in children may prompt genetic testing. This can influence therapeutic plans. Therefore, imaging features could potentially be incorporated into CMMRD testing recommendations.Using imaging to detect CMMRD syndrome early may improve patient care.CMMRD features include: hemispheric HGG with multiple developmental venous anomalies and NF1-like or subcortical areas with high T2-FLAIR intensity.We propose novel imaging features to improve the identification of potential CMMRD patients.Using imaging to detect CMMRD syndrome early may improve patient care.CMMRD features include: hemispheric HGG with multiple developmental venous anomalies and NF1-like or subcortical areas with high T2-FLAIR intensity.We propose novel imaging features to improve the identification of potential CMMRD patients. [ABSTRACT FROM AUTHOR]