Myxoid glioneuronal tumor: Histopathologic, neuroradiologic, and molecular features in a single center series

Rosette-Forming Glioneuronal Tumor Mimicking Foramen Monro Colloid Cyst: Case Presentation and Systematic Literature Review

BACKGROUND

Rosette-forming glioneuronal tumors (RGNTs) are rare indolent and benign tumors, typically associated with the fourth ventricle. Cases in the third ventricle are less common, especially those involving only the anterior part.

METHODS

A literature review using "rosette-forming glioneuronal tumor" on PubMed yielded 176 articles from 2002 to 2024. Articles excluding third ventricle RGNTs were omitted, with titles and abstracts screened for relevance. We also present our case of an anterior third ventricle RGNT, tracking from initial presentation to follow-up.

RESULTS

Our patient, a 62-year-old woman, experienced 3 months of recurrent Hakim Triad symptoms-gait instability, urinary incontinence, and cognitive issues. Magnetic resonance imaging revealed a 1.0 × 0.7 cm mass, hypointense on T1-weighted imaging and heterogeneous on T2-weighted imaging, initially suspected as a colloid cyst. Given its high colloid cyst risk score, surgery was performed, but histopathology confirmed an RGNT diagnosis. To date, this is the first case of exclusive anterior third ventricle RGNT microsurgery reported, with 26 months of recurrence-free follow-up. Our literature review identified 20 articles detailing 23 cases of third ventricle RGNT, with only 7 achieving gross total resection, while most underwent biopsy and ventriculostomy.

CONCLUSIONS

RGNTs in the anterior third ventricle may resemble other tumor types, requiring careful monitoring. This case is significant due to the patient's clinical presentation, imaging, and extended recurrence-free follow-up.

Clinical characteristics, molecular reclassification trajectories and DNA methylation patterns of long- and short-term survivors of WHO grade II and III glioma

PURPOSE

The prognosis of diffuse gliomas previously classified as "lower-grade" is heterogeneous and complicates clinical decisions. We aimed to investigate the molecular profile of clinical outliers to gain insight into biological drivers of long and short-term survivors.

METHODS

Here, patients aged ≥ 18 years and diagnosed with diffuse glioma, WHO grade II/2 or III/3 were included. Short-term survivors (STS) were defined as overall survival (OS) < 1 years, and long-term survivors (LTS) as OS > 10 years. DNA methylation profiling was performed using the Illumina EPIC 850k platform.

RESULTS

In total, 385 patients (294 LTS, 91 STS) were included. Median overall survival was 234 months (95%CI: 207-248) in LTS and 7.3 months (95%CI: 6.4-8.1) in STS. Compared to STS, LTS were younger, had higher Karnofsky Performance Status, more extensive resections, and lower symptomatic burden (p < 0.001, respectively). Molecular reclassification showed IDH-mutant gliomas in 240/246 (95.5%) LTS and 10/79 (12.7%) STS. Initial diagnosis (tumor type and/or grading) changed in 69/325 (21.2%) patients based on reclassification according to WHO 2016 and in 45/258 (17.4%) as per WHO 2021. DNA methylation analysis indicated two clusters, one with mainly STS (39/41, 95.1%) and heterogeneous IDH-wildtype tumors (cluster A) and one with mainly LTS (82/106, 77.4%) and IDH-mutant tumors (cluster B). Functional enrichment analysis of rare subtypes indicated altered Hippo/Notch and synaptic/neurotransmitter signaling pathway members.

CONCLUSION

LTS and STS show distinct clinical and molecular features, underscoring the importance of extended molecular workup for diagnosis. Further characterization of rare subtypes is needed to optimize treatment strategies and clinical trial planning.

Chromosomal gain and mutations of platelet-derived growth factor receptor-α gene in canine high-grade oligodendroglioma

Canine high-grade oligodendrogliomas (HGOGs) exhibit a high expression of platelet-derived growth factor receptor-α (PDGFRA). We examined PDGFRA mutations and gain of PDGFRA and their association with the PDGFRA expression and proliferation of tumor cells in canine HGOG cases and cell lines. Polymerase chain reaction and sequence analysis revealed expected pathogenic mutations in PDGFRA exons 7 and 8 in 16/34 (47%) cases. However, these mutations were not associated with PDGFRA expression, as examined by mRNA in situ hybridization (ISH) and immunohistochemistry, or proliferation activity, as examined by the Ki-67 labeling index (LI). Chromosomal ISH performed in 16 cases revealed PDGFRA and endoplasmic reticulum membrane protein complex subunit 2 (EMC2) gains in 15 cases (94%). PDGFRA gain was moderately correlated with PDGFRA mRNA expression (ρ = 0.54, P = .04) and were moderately correlated with PDGFRA H-score, which is the score based on immunolabeling intensity (ρ = 0.44, P = .09). However, PDGFRA gain was not correlated with the Ki-67 LI (ρ = 0.23, P = .38). The canine HGOG cell line with PDGFRA gain showed higher PDGFRA mRNA expression (P < .01), H-score (P < .01), and Ki-67 LI (P < .01) than the cell line without PDGFRA gain in vitro. The gain of PDGFRA and EMC2 suggests polysomy of canine chromosome 13, where both genes are located. The in vitro analysis results suggested that chromosome 13 polysomy is associated with increased PDGFRA expression and cell proliferation in canine HGOG. Chromosome 13 polysomy may be involved in canine gliomagenesis by increasing PDGFRA expression and inducing tumor cell proliferation.

Novel insights toward diagnosis and treatment of glioneuronal and neuronal tumors in young adults

Aim: Glioneuronal and neuronal tumors are rare primary central nervous system malignancies with heterogeneous features. Due to the rarity of these malignancies diagnosis and treatment remains a clinical challenge. Methods: Here we performed a narrative review aimed to investigate the principal issues concerning the diagnosis, pathology, and clinical management of glioneuronal tumors. Results: Diagnostic criteria have been recently overturned thanks to a better characterization on a histological and molecular biology level. The study of genomic alterations occurring within these tumors has allowed us to identify potential therapeutic targets including BRAF, FGFR, and PDGFRA. Conclusion: Techniques allowing molecular sequencing DNA methylation assessment of the disease are essential diagnostic tools. Targeting agents should be included in the therapeutic armamentarium after loco-regional treatment failure.

Myxoid glioneuronal tumor of the septum pellucidum in pediatric patients: a case report and comprehensive review of the literature

INTRODUCTION

Myxoid glioneuronal tumor of the septum pellucidum is an uncommon clinical entity, previously referred to dysembryoplastic neuroepithelial tumor located in the septum pellucidum.

METHODS

This study was conducted following PRISMA guidelines. A comprehensive literature search was performed in the PubMed/MEDLINE, Web of Science, and Scopus databases. In addition to the literature review, we report a rare case of a 10-year-old male patient with septal myxoid glioneuronal tumor who underwent endoscopic tumor resection as an exemplary case.

RESULTS

A total of 10 pediatric patients from 7 published records were included in this review. An analysis encompassing 11 patients, including the present patient, was performed. The mean age of the patients was 11.36 ± 3.35 years, with a male predominance. The most common presenting symptoms were headache (50%), and seizures (37.5%). Nine patients had microsurgical tumor resection, while 2 patients underwent endoscopic tumor resection. Seven patients underwent gross total or near total resection, while 4 had subtotal resection, and the prognosis for all patients was good.

CONCLUSION

Myxoid glioneuronal tumor of the septum pellucidum represents a rare and relatively benign pathology with typical localization and histopathological features. Surgical resection is the primary treatment modality, aiming for maximal safe resection while preserving neurological function. However, complete resection may not always be achievable due to the infiltrative nature of these tumors and their proximity to critical structures. Generally, the prognosis for these tumors is favorable.

Imaging of pediatric glioneuronal and neuronal tumors

Glioneuronal tumors (GNTs) are an expanding group of primary CNS neoplasms, commonly affecting children, adolescents and young adults. Most GNTs are relatively indolent, low-grade, WHO grade I lesions. In the pediatric age group, GNTs have their epicenter in the cerebral cortex and present with seizures. Alterations in the mitogen-activated protein kinase (MAPK) pathway, which regulates cell growth, are implicated in tumorigenesis. Imaging not only plays a key role in the characterization and pre-surgical evaluation of GNTs but is also crucial role in follow-up, especially with the increasing use of targeted inhibitors and immunotherapies. In this chapter, we review the clinical and imaging perspectives of common pediatric GNTs.

PDGFRA K385 mutants in myxoid glioneuronal tumors promote receptor dimerization and oncogenic signaling

Myxoid glioneuronal tumors (MGNT) are low-grade glioneuronal neoplasms composed of oligodendrocyte-like cells in a mucin-rich stroma. These tumors feature a unique dinucleotide change at codon 385 in the platelet-derived growth factor receptor α (encoded by the PDGFRA gene), resulting in the substitution of lysine 385 into leucine or isoleucine. The functional consequences of these mutations remain largely unexplored. Here, we demonstrated their oncogenic potential in fibroblast and Ba/F3 transformation assays. We showed that the K385I and K385L mutants activate STAT and AKT signaling in the absence of ligand. Co-immunoprecipitations and BRET experiments suggested that the mutations stabilized the active dimeric conformation of the receptor, pointing to a new mechanism of oncogenic PDGF receptor activation. Furthermore, we evaluated the sensitivity of these mutants to three FDA-approved tyrosine kinase inhibitors: imatinib, dasatinib, and avapritinib, which effectively suppressed the constitutive activity of the mutant receptors. Finally, K385 substitution into another hydrophobic amino acid also activated the receptor. Interestingly, K385M was reported in a few cases of brain tumors but not in MGNT. Our results provide valuable insights into the molecular mechanism underlying the activation of PDGFRα by the K385I/L mutations, highlighting their potential as actionable targets in the treatment of myxoid glioneuronal tumors.

Memory deficit following resection of an intraventricular myxoid glioneuronal tumor impinging on the bilateral fornix: A case report

Background

Recently recognized as a distinct entity, a myxoid glioneuronal tumor (MGNT) is a rare, low-grade central nervous system tumor. MGNTs are commonly located at the septum pellucidum or in the third ventricle, increasing the likelihood of tumor or treatment-related damage to adjacent structures critical for memory, such as the fornix. Though there have been a handful of case reports of neurosurgical and oncological outcomes of MGNTs, memory outcomes following resection of MGNTs adjacent to the fornix have not been previously reported.

Methods

We present a case of a high functioning female for whom an MRI revealed an incidental finding of an intraventricular tumor adjacent to the fornix bilaterally. The patient underwent resection of the tumor followed by MRI surveillance without additional oncologic intervention. Due to reported cognitive problems, the patient was referred for serial neuropsychological evaluations.

Results

Post-operative MRI following resection revealed cytotoxic edema followed by selective, progressive atrophy of the bilateral anterior fornices. Post-surgically, the patient developed an isolated verbal memory impairment, which persisted one-year post resection with minimal improvement. The memory impairment impacted the patient's everyday functioning, including the ability to work in a cognitively demanding job.

Conclusion

This unique case demonstrates the critical role of the bilateral fornix in verbal memory and underscores the importance of a careful risk/benefit analysis when considering neurosurgical intervention to MGNTs and other intracranial lesions adjacent to this structure during neurosurgical planning.