Rosette-forming glioneuronal tumours are midline, FGFR1-mutated tumours

H3 K27M mutation in rosette-forming glioneuronal tumors: a potential diagnostic pitfall

According to the fifth edition of the World Health Organization (WHO) classification of tumors of the central nervous system (CNS), diffuse midline glioma H3 K27-altered is a grade 4 infiltrative glioma that arises from midline anatomical structures and is characterized by the loss of H3 K27me3 and co-occurring H3 K27M mutation or EZHIP overexpression. However, the H3 K27M mutation has also been observed in circumscribed gliomas and glioneuronal tumors arising in midline anatomical structures, which may result in diagnostic pitfalls.Rosette-forming glioneuronal tumor (RGNT) is a CNS WHO grade 1 neoplasm that histologically features neurocytic and glial components and originates in midline anatomical structures.This study aimed to assess whether RGNTs, similar to other midline tumors, may exhibit immunohistochemical loss of H3 K27me3 and harbor the H3 K27M mutation.All seven analyzed RGNTs displayed immunohistochemical loss of H3 K27me3 in all tumor cells or H3 K27me3 mosaic immunostaining. In one case, H3 K27me3 loss was associated with the H3 K27M mutation, whereas the other six cases did not exhibit any H3 mutations or EZHIP overexpression. During a follow-up period of 23 months, the H3 K27M-mutant case remained unchanged in size despite partial resection, indicating that the H3 mutation may not confer higher biological aggressiveness to RGNT.The immunohistochemical loss of H3 K27me3 co-occurring with the H3 K27M mutation may result in the potential misdiagnosis of RGNT, especially in cases of small biopsy specimens consisting of only the glial component.

Multinodular and Vacuolating Neuronal Tumors: Imaging Features, Diagnosis, and Management Challenges

Background/Objectives: Multinodular and vacuolating neuronal tumors (MNVTs) are a type of recently identified benign neuroepithelial tumor with debated malformative or neoplastic origins. This review summarizes their neuroanatomical localization, imaging, histopathology, immunohistochemistry, and diagnostic challenges. Methods: A systematic review of PUBMED/MEDLINE was performed in December 2024. Results: Of 118 screened articles, 39 were eligible, covering 299 patients. MNVTs are often asymptomatic "leave me alone" lesions, discovered incidentally, though nonspecific symptoms (59.9%) and seizures (19.7%) are reported. Immunohistochemistry reveals variable profiles, reflecting complex cellular differentiation. The characteristic "bubble-like" MRI pattern along the subcortical ribbon and superficial white matter is a reliable diagnostic feature. Rare cortical involvement and atypical band-like lesions occur. MRI signal intensity varies. Over a mean follow-up of 36 months, lesions were stable or non-recurrent, with only one case of progression. Conclusion: MVNT imaging mimics other glioneuronal lesions, but reliable diagnostic MRI features include a "bubble-clustered" appearance, lack of cortical involvement, absence of enhancement, and temporal lobe predominance. Hemodynamic and metabolic properties support the diagnosis. Most lesions remain stable, requiring no treatment. Surgical resection is reserved for cases with uncontrolled seizures or atypical locations where the diagnosis is unclear.

A glioneuronal tumor with neurocytic rosettes harboring FGFR1 internal tandem duplication - A report of a unique case

Rosette-forming glioneuronal tumors (RGNTs) with FGFR1 tyrosine kinase domain internal tandem duplication (FGFR1 ITD) is exceedingly rare, with only a few cases reported in the literature. Hereby we present a case of a tumor with RGNT morphology occurring in area of septum pellucidum of 43-year-old male. The tumor showed FGFR1 ITD, no PIK3CA, PIK3R1 or NF1 alterations and inconclusive methylation profile with match for class of "low-grade glial/glioneuronal/neuroepithelial tumors". No areas characteristic of dysembryoplastic neuroepithelial tumor were identified. A brief review of literature on discrepancies between morphological diagnosis of RGNT and molecular profile of the entity is provided.

The Clinical and Molecular Landscape of Rosette-Forming Glioneuronal Tumors

BACKGROUND

Rosette-Forming Glioneuronal Tumors (RGNTs) are rare, typically benign central nervous system tumors primarily located in the fourth ventricle and pineal region. Despite being classified as WHO grade I with generally favorable prognoses, RGNTs present complexities in their molecular mechanisms, occasional malignant transformation, and epidemiological characteristics that require further investigation.

METHOD

This study systematically reviews the existing literature to analyze the epidemiological patterns, MRI characteristics, pathological features, diagnostic challenges, and molecular mechanisms associated with RGNTs, aiming to provide a comprehensive theoretical foundation for clinical practice and future research.

RESULTS

Through an in-depth review of recent studies, key molecular mechanisms, including mutations in FGFR1, PIK3CA, TERT, and IDH1/2, are highlighted. Additionally, the challenges in accurate diagnosis and the potential for misdiagnosis are discussed, emphasizing the importance of thorough molecular analysis in clinical settings. The literature indicates that RGNTs predominantly affect young adults and adolescents, with a slight female predominance. MRI typically reveals mixed cystic-solid lesions, often accompanied by hydrocephalus. Pathologically, RGNTs are characterized by a combination of neuronal and glial components, with immunohistochemical staining showing positivity for Synaptophysin and GFAP. High frequencies of FGFR1 and PIK3CA mutations underscore the significance of these pathways in RGNT pathogenesis and progression. Although RGNTs generally exhibit low malignancy, the TERT mutations identified in some cases suggest a risk of malignant transformation.

CONCLUSIONS

This study concludes that while current treatment strategies focus on surgical resection, integrating molecular diagnostics and targeted therapies may be essential for managing recurrent or refractory RGNTs. Future research should explore the impact of various gene mutations on tumor behavior and their correlation with clinical outcomes, to optimize individualized therapeutic strategies and improve patient survival and quality of life.

Paediatric low-grade glioma: the role of classical pathology in integrated diagnostic practice

Low-grade gliomas are a cause of severe and often life-long disability in children. Pathology plays a key role in their management by establishing the diagnosis, excluding malignant alternatives, predicting outcomes and identifying targetable genetic alterations. Molecular diagnosis has reshaped the terrain of pathology, raising the question of what part traditional histology plays. In this review, we consider the classification and pathological diagnosis of low-grade gliomas and glioneuronal tumours in children by traditional histopathology enhanced by the opportunities afforded by access to comprehensive genetic and epigenetic characterisation.

Molecular characterization of gliomas and glioneuronal tumors amid Noonan syndrome: cancer predisposition examined

Introduction

In the setting of pediatric and adolescent young adult cancer, increased access to genomic profiling has enhanced the detection of genetic variation associated with cancer predisposition, including germline syndromic conditions. Noonan syndrome (NS) is associated with the germline RAS pathway activating alterations and increased risk of cancer. Herein, we describe our comprehensive molecular profiling approach, the association of NS with glioma and glioneuronal tumors, and the clinical and histopathologic characteristics associated with the disease.

Methods

Within an institutional pediatric cancer cohort (n = 314), molecular profiling comprised of paired somatic disease-germline comparator exome analysis, RNA sequencing, and tumor classification by DNA methylation analysis was performed.

Results

Through the implementation of paired analysis, this study identified 4 of 314 (1.3%) individuals who harbored a germline PTPN11 variant associated with NS, of which 3 individuals were diagnosed with a glioma or glioneuronal tumor. Furthermore, we extend this study through collaboration with a peer institution to identify two additional individuals with NS and a glioma or glioneuronal tumor. Notably, in three of five (60%) individuals, paired genomic profiling led to a previously unrecognized diagnosis of Noonan syndrome despite an average age of cancer diagnosis of 16.8 years. The study of the disease-involved tissue identified signaling pathway dysregulation through somatic alteration of genes involved in cellular proliferation, survival, and differentiation.

Discussion

Comparative pathologic findings are presented to enable an in-depth examination of disease characteristics. This comprehensive analysis highlights the association of gliomas and glioneuronal tumors with RASopathies and the potential therapeutic challenges and importantly demonstrates the utility of genomic profiling for the identification of germline cancer predisposition.

Pediatric low-grade glioma models: advances and ongoing challenges

Pediatric low-grade gliomas represent the most common childhood brain tumor class. While often curable, some tumors fail to respond and even successful treatments can have life-long side effects. Many clinical trials are underway for pediatric low-grade gliomas. However, these trials are expensive and challenging to organize due to the heterogeneity of patients and subtypes. Advances in sequencing technologies are helping to mitigate this by revealing the molecular landscapes of mutations in pediatric low-grade glioma. Functionalizing these mutations in the form of preclinical models is the next step in both understanding the disease mechanisms as well as for testing therapeutics. However, such models are often more difficult to generate due to their less proliferative nature, and the heterogeneity of tumor microenvironments, cell(s)-of-origin, and genetic alterations. In this review, we discuss the molecular and genetic alterations and the various preclinical models generated for the different types of pediatric low-grade gliomas. We examined the different preclinical models for pediatric low-grade gliomas, summarizing the scientific advances made to the field and therapeutic implications. We also discuss the advantages and limitations of the various models. This review highlights the importance of preclinical models for pediatric low-grade gliomas while noting the challenges and future directions of these models to improve therapeutic outcomes of pediatric low-grade gliomas.

Deciphering the Action of Neuraminidase in Glioblastoma Models

Glioblastoma (GBM) contains cancer stem cells (CSC) that are resistant to treatment. GBM CSC expresses glycolipids recognized by the A2B5 antibody. A2B5, induced by the enzyme ST8 alpha-N-acetyl-neuraminide alpha-2,8-sialyl transferase 3 (ST8Sia3), plays a crucial role in the proliferation, migration, clonogenicity and tumorigenesis of GBM CSC. Our aim was to characterize the resulting effects of neuraminidase that removes A2B5 in order to target GBM CSC. To this end, we set up a GBM organotypic slice model; quantified A2B5 expression by flow cytometry in U87-MG, U87-ST8Sia3 and GBM CSC lines, treated or not by neuraminidase; performed RNAseq and DNA methylation profiling; and analyzed the ganglioside expression by liquid chromatography-mass spectrometry in these cell lines, treated or not with neuraminidase. Results demonstrated that neuraminidase decreased A2B5 expression, tumor size and regrowth after surgical removal in the organotypic slice model but did not induce a distinct transcriptomic or epigenetic signature in GBM CSC lines. RNAseq analysis revealed that OLIG2, CHI3L1, TIMP3, TNFAIP2, and TNFAIP6 transcripts were significantly overexpressed in U87-ST8Sia3 compared to U87-MG. RT-qPCR confirmed these results and demonstrated that neuraminidase decreased gene expression in GBM CSC lines. Moreover, neuraminidase drastically reduced ganglioside expression in GBM CSC lines. Neuraminidase, by its pleiotropic action, is an attractive local treatment against GBM.

Clinico-pathological and epigenetic heterogeneity of diffuse gliomas with FGFR3::TACC3 fusion

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.

The landscape of common genetic drivers and DNA methylation in low-grade (epilepsy-associated) neuroepithelial tumors: A review

Low-grade neuroepithelial tumors (LNETs) represent an important group of central nervous system neoplasms, some of which may be associated to epilepsy. The concept of long-term epilepsy-associated tumors (LEATs) includes a heterogenous group of low-grade, cortically based tumors, associated to drug-resistant epilepsy, often requiring surgical treatment. LEATs entities can sometimes be poorly discriminated by histological features, precluding a confident classification in the absence of additional diagnostic tools. This study aimed to provide an updated review on the genomic findings and DNA methylation profiling advances in LNETs, including histological entities of LEATs. A comprehensive search strategy was conducted on PubMed, Embase, and Web of Science Core Collection. High-quality peer-reviewed original manuscripts and review articles with full-text in English, published between 2003 and 2022, were included. Results were screened based on titles and abstracts to determine suitability for inclusion, and when addressed the topic of the review was screened by full-text reading. Data extraction was performed through a qualitative content analysis approach. Most LNETs appear to be driven mainly by a single genomic abnormality and respective affected signaling pathway, including BRAF p.V600E mutations in ganglioglioma, FGFR1 abnormalities in dysembryoplastic neuroepithelial tumor, MYB alterations in angiocentric glioma, BRAF fusions in pilocytic astrocytoma, PRKCA fusions in papillary glioneuronal tumor, between others. However, these molecular alterations are not exclusive, with some overlap amongst different tumor histologies. Also, clustering analysis of DNA methylation profiles allowed the identification of biologically similar molecular groups that sometimes transcend conventional histopathological classification. The exciting developments on the molecular basis of these tumors reinforce the importance of an integrative histopathological and (epi)genetic classification, which can be translated into precision medicine approaches.