Fourth ventricle rosette-forming glioneuronal tumour in children: an unusual presentation in an 8-year-old patient, discussion and review of the literature

The 2021 WHO Classification for Gliomas and Implications on Imaging Diagnosis: Part 3-Summary of Imaging Findings on Glioneuronal and Neuronal Tumors

The fifth edition of the World Health Organization classification of central nervous system tumors published in 2021 reflects the current transitional state between traditional classification system based on histopathology and the state-of-the-art molecular diagnostics. This Part 3 Review focuses on the molecular diagnostics and imaging findings of glioneuronal and neuronal tumors. Histological and molecular features in glioneuronal and neuronal tumors often overlap with pediatric-type diffuse low-grade gliomas and circumscribed astrocytic gliomas (discussed in the Part 2 Review). Due to this overlap, in several tumor types of glioneuronal and neuronal tumors the diagnosis may be inconclusive with histopathology and genetic alterations, and imaging features may be helpful to distinguish difficult cases. Thus, it is crucial for radiologists to understand the underlying molecular diagnostics as well as imaging findings for application on clinical practice. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 3.

Other Less Prevalent Tumors of the Central Nervous System

The presented tumors in this chapter are somewhat very rare, and their management is still debated due to the scarcity of information about their cell of origin, behavior, and biology. Treatment options are still limited, but we are confident that in the near future by discovering the genetic and biological mechanisms that drive tumor growth we will be able to offer new target therapies that should be flanked by surgery, radiotherapy, and chemotherapeutic agents actually in use. The purpose of this chapter is to highlight the most important known characteristics of these tumors offering the chance to recognize the disease and then offer the best opportunity for treatment to patients. The 5th WHO Classification Central Nervous System features substantial changes by moving further to advance the role of molecular diagnostics in CNS tumor classification, but remaining rooted in other established approaches to tumor characterization, including histology and immunohistochemistry, and probably, the category of many tumors will change. Here, the most important characteristics of each neoplasm are summarized focusing on genetic mechanisms and molecular pathways, their histopathologic footprints, signs and symptoms, radiologic features, therapeutic approaches, and prognosis as well as follow-up protocols. Schematic classifications are also presented to offer a better understanding of the pathology.

Immune Microenvironment and Lineage Tracing Help to Decipher Rosette-Forming Glioneuronal Tumors: A Multi-Omics Analysis

Rosette-forming glioneuronal tumors (RGNT) are rare low-grade primary central nervous system (CNS) tumors. The methylation class (MC) RGNT (MC-RGNT) delineates RGNT from other neurocytic CNS tumors with similar histological features. We performed a comprehensive molecular analysis including whole-exome sequencing, RNAseq, and methylome on 9 tumors with similar histology, focusing on the immune microenvironment and cell of origin of RGNT. Three RGNT in this cohort were plotted within the MC-RGNT and characterized by FGFR1 mutation plus PIK3CA or NF1 mutations. RNAseq analysis, validated by immunohistochemistry, identified 2 transcriptomic groups with distinct immune microenvironments. The "cold" group was distinguishable by a low immune infiltration and included the 3 MC-RGNT and 1 MC-pilocytic astrocytoma; the "hot" group included other tumors with a rich immune infiltration. Gene set enrichment analysis showed that the "cold" group had upregulated NOTCH pathway and mainly oligodendrocyte precursor cell and neuronal phenotypes, while the "hot" group exhibited predominantly astrocytic and neural stem cell phenotypes. In silico deconvolution identified the cerebellar granule cell lineage as a putative cell of origin of RGNT. Our study identified distinct tumor biology and immune microenvironments as key features relevant to the pathogenesis and management of RGNT.

Rosette-Forming Glioneuronal Tumor of the Fourth Ventricle: A Case of Relapse Treated with Proton Beam Therapy

Rosette-forming glioneuronal tumors (RGNTs) are rare, grade I, central nervous system (CNS) tumors typically localized to the fourth ventricle. We describe a 9-year-old girl with dizziness and occipital headache. A magnetic resonance imaging (MRI) revealed a large hypodense posterior fossa mass lesion in relation to the vermis, with cystic component. Surgical resection of the tumor was performed. A RGNT diagnosis was made at the histopathological examination. During follow-up, the patient experienced a first relapse, which was again surgically removed. Eight months after, MRI documented a second recurrence at the local level. She was a candidate for the proton beam therapy (PBT) program. Three years after the end of PBT, the patient had no evidence of disease recurrence. This report underlines that, although RGNTs are commonly associated with an indolent course, they may have the potential for aggressive behavior, suggesting the need for treatment in addition to surgery. Controversy exists in the literature regarding effective management of RGNTs. Chemotherapy and radiation are used as adjuvant therapy, but their efficacy management has not been adequately described in the literature. This is the first case report published in which PBT was proposed for adjuvant therapy in place of chemotherapy in RGNT relapse.

Rosette-forming Glioneuronal Tumor in the Optic Pathway of a Child

Rosette-forming glioneuronal tumor is a rare World Health Organization grade I neoplasm, primarily involving the posterior fossa. Most cases have been reported in young adults. Although maximal surgical resection is advocated, a precise treatment modality is yet to be established. We describe an unusual presentation of rosette-forming glioneuronal tumor occurring in the optic pathway in a child. As the site of the tumor was not amenable to resection, he underwent radiotherapy and is currently well on follow-up.

Rosette-forming glioneuronal tumor: an illustrative case and a systematic review

Background

Rosette-forming glioneuronal tumors (RGNTs) are rare, low-grade, primary CNS tumors first described in 2002 by Komori et al. RGNTs were initially characterized as a World Health Organization (WHO) grade I tumors typically localized to the fourth ventricle. Although commonly associated with an indolent course, RGNTs have the potential for aggressive behavior.

Methods

A comprehensive search of PubMed and Web of Science was performed through November 2019 using the search term “rosette-forming glioneuronal tumor.” Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. English, full-text case reports and series with histopathological confirmation were included. Patient demographics, presentations, MRI features, tumor location, treatment, and follow-up of all 130 cases were extracted.

Results

A 19-year-old man with a history of epilepsy and autism presented with acute hydrocephalus. MRI scans from 2013 to 2016 demonstrated unchanged abnormal areas of cortex in the left temporal lobe with extension into the deep gray-white matter. On presentation to our clinic in 2019, the lesion demonstrated significant progression. The patient’s tumor was identified as RGNT, WHO grade I. One hundred thirty patients were identified across 80 studies.

Conclusion

RGNT has potential to transform from an indolent tumor to a tumor with more aggressive behavior. The results of our systematic review provide insight into the natural history and treatment outcomes of these rare tumors.

Histopathological, molecular, clinical and radiological characterization of rosette-forming glioneuronal tumor in the central nervous system

Objective

A rosette-forming glioneuronal tumor (RGNT) is a rare entity originally described in the fourth ventricle. Recently, RGNTs occurring in extraventricular sites and those with malignant behaviors have been reported. The purpose of this study was to analyze the clinicoradiological and histopathological features, therapeutic strategies, and outcomes of RGNTs.

Methods

We enrolled 38 patients diagnosed with RGNTs pathologically between August 2009 and June 2016. CT and MRI, including diffusion-weighted imaging and spectroscopy, were performed. The surgical treatment and histopathological and molecular features were assessed. Additionally, we searched the relevant literatures and performed a pooled analysis of individual patient data. The potential risk factors of prognosis were analyzed.

Results

Our case series included 22 male and 16 female patients, with a mean age of 25.9 years. RGNTs involved the fourth ventricle (26.3%), cerebella (34.2%), supratentorial ventricular system (13.2%), spinal cord (10.5%), temporal lobe (10.5%), thalamus (7.9%), brain stem (7.9%), frontal lobe (5.3%), pineal region (5.3%), suprasellar region (2.6%), and basal ganglia (2.6%). Statistical analyses showed that pediatric age, purely solid appearance of the tumor, and inadequate resection (only partial removal or biopsy) were risk factors associated with progression events. Patients with subtotal resection appeared to do as well as those with gross total resection.

Conclusions

RGNTs can occur nearly anywhere in the CNS, at both supratentorial and infratentorial sites. Maximal safe surgical resection should be emphasized for treatment; whilst aggressive resection with the goal of complete resection may be unnecessary.

Rosette-Forming Glioneuronal Tumor of the Fourth Ventricle in Children: Case Report and Literature Review

BACKGROUND

Rosette-forming glioneuronal tumor (RGNT) of the fourth ventricle is a rare World Health Organization (WHO) grade I neoplasm. Gross total resection (GTR) is the treatment of choice, and there is no firm evidence supporting other treatment options when GTR is not feasible.

CASE DESCRIPTION

We report a 6-year-old boy who, following an initial subtotal resection of a fourth ventricular RGNT, received an individualized chemotherapy protocol with vincristine, etoposide, and carboplatin for 3 cycles. The tumor was stable for 2 years after the completion of chemotherapy but then began to progress, at which point GTR was successfully performed. In addition, we completed a comprehensive literature review of RGNT cases. To date, a total of 104 cases have been reported, 33 of which are pediatric cases. Recurrence has been reported in only 7 cases of all ages (4 in the pediatric population). Radiotherapy has been used in several cases, but adjuvant chemotherapy has been reported only once following a recurrence.

CONCLUSIONS

We report a case of chemotherapy administration as a first-line treatment for a subtotally resected RGNT. Chemotherapy may be considered as an adjuvant therapy option for RGNT when GTR cannot be achieved. Furthermore, increased incidence of recurrence in the pediatric population may suggest that the tumor biology of RGNT in children differs from that in adults.

Rosette-forming glioneuronal tumor outside the fourth ventricle: a case-based update

INTRODUCTION

Rosette-forming glioneuronal tumors (RGNTs) that do not involve the fourth ventricle are rare. RGNTs were originally thought to be exclusively localized into the fourth ventricle but were found in various anatomical localizations.

MATERIAL AND METHODS

We review the literature and found 32 cases of this particular RGNT. The outcome was excellent with no mortality reported after surgical treatment. Only two patients had received adjuvant therapy for progression. We added one case of a RGNT located in the cerebellar hemisphere.

CASE AND CONCLUSION

She underwent a subtotal removal with no evidence of progression after. This WHO grade I tumor with a specific biphasic histopathology is of a good oncological outcome after surgical treatment. A long follow-up is needed as recurrence or metastatic progressions exist.

Molecular Profiling of a Rare Rosette-Forming Glioneuronal Tumor Arising in the Spinal Cord

Rosette-forming glioneuronal tumor (RGNT) of the IV ventricle is a rare and recently recognized brain tumor entity. It is histologically composed by two distinct features: a glial component, resembling pilocytic astrocytoma, and a component forming neurocytic rosettes and/or perivascular rosettes. Herein, we describe a 33-year-old man with RGNT arising in the spinal cord. Following an immunohistochemistry validation, we further performed an extensive genomic analysis, using array-CGH (aCGH), whole exome and cancer-related hotspot sequencing, in order to better understand its underlying biology. We observed the loss of 1p and gain of 1q, as well as gain of the whole chromosomes 7, 9 and 16. Local amplifications in 9q34.2 and 19p13.3 (encompassing the gene SBNO2) were identified. Moreover, we observed focal gains/losses in several chromosomes. Additionally, on chromosome 7, we identified the presence of the KIAA1549:BRAF gene fusion, which was further validated by RT-PCR and FISH. Across all mutational analyses, we detected and validated the somatic mutations of the genes MLL2, CNNM3, PCDHGC4 and SCN1A. Our comprehensive molecular profiling of this RGNT suggests that MAPK pathway and methylome changes, driven by KIAA1549:BRAF fusion and MLL2 mutation, respectively, could be associated with the development of this rare tumor entity.

Rosette-forming glioneuronal tumor originating in the hypothalamus

Rosette-forming glioneuronal tumors (RGNT) of the fourth ventricle are slow-growing tumors that primarily involve the fourth ventricular region. We here report the first patient, an 8-year-old girl, with an RGNT originating in the hypothalamus and manifesting with precocious puberty. After partial removal, the remaining tumor showed rapid enlargement, and the pathologic diagnosis at the second surgery revealed histopathologic features similar to those found in the initial samples, including biphasic patterns of neurocytic rosettes and GFAP-stained astrocytic components. These tumor cells had mildly atypical nuclei; however, mitotic figures and necrosis were absent. Eosinophilic granular bodies and a glomeruloid vasculature were found, but Rosenthal fibers were absent. The Ki-67 proliferative index was 3.5 % (vs 1.1 % at the initial surgery). No recurrence was recorded during the 3-year period after the proton radiotherapy.