Rosette-forming glioneuronal tumor: a pineal region case with IDH1 and IDH2 mutation analyses and literature review of 43 cases

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.

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.

Diffusely invasive supratentorial rosette-forming glioneuronal tumor: illustrative case

BACKGROUND

Rosette-forming glioneuronal tumors (RGNTs) are rare tumors composed of mixed glial and neurocytic components. Most lesions are confined to the posterior fossa, especially in the region of the fourth ventricle, in young adults. In few instances, diffuse involvement of the supratentorial region is identified, thereby creating significant challenges in diagnosis, surgical intervention, and prognostication.

OBSERVATIONS

The authors present a 23-year-old female with chronic headaches, papilledema, and hydrocephalus who underwent radiographic evaluation revealing obstructive hydrocephalus and diffuse supratentorial enhancing and nonenhancing cystic and nodular lesions. The patient underwent a right frontal craniotomy and septostomy. An exophytic nonenhancing right frontal horn lesion was resected, and an enhancing third-ventricular lesion was biopsied. Final pathology of both of the lesions sampled was consistent with RGNT. Next-generation sequencing demonstrated tumor alterations in the FGFR-1 and PIK3CA genes. Targeted therapy with the FGFR inhibitor erdafitinib demonstrated a partial remission.

LESSONS

Diffuse supratentorial spread of RGNT is an extremely rare presentation of an already uncommon pathology. In some cases, gross-total resection may not be feasible. Goals of surgery include acquiring tissue for diagnosis, maximizing safe resection, and treating any associated hydrocephalus. FGFR inhibitors may be of benefit in cases of disease progression.

Recurrent anaplastic transformation of a Vermian region rosette forming glioneuronal tumour – A rare entity. Case report and review of literature

INTRODUCTION AND IMPORTANCE

Rosette forming Glioneuronal tumours (RGNT) are rare WHO grade I tumours. They have been recognised as a sole entity in the WHO classification since 2007. They are typically described as having a favourable prognosis. Since their description as a distinct entity, there have been only four reports of malignant or anaplastic transformation of RGNT. We report a case of recurrent RGNT with new anaplastic histopathological features.

CASE PRESENTATION

We present the case of a 48-year-old female who presented with a vermian region RGNT. The tumour recurred six years after initial surgical resection with new anaplastic transformation. Despite further surgery, chemotherapy, and radiation, the lesion continued to recur with high grade features.

CLINICAL DISCUSSION

RGNT is a rare variant of a mixed glial-neuronal tumour. It has been defined as a WHO grade I lesion with a favourable prognostic course. There is growing evidence that this neoplasm can demonstrate malignant transformation with aggressive behaviour.

CONCLUSION

Recurrent RGNT is a rare entity. There is a growing bank of literature surrounding this relatively new entity to aid patients and clinicians alike in management decisions. To our knowledge, we report one of only few cases of anaplastic transformation of a RGNT. A high degree of suspicion should be maintained for patients with recurrent RGNT and in suitable cases, surgical resection with adjuvant chemo-irradiation should be pursued.

Large pineal parenchymal tumor of intermediate differentiation causing compression with resultant obstructive hydrocephalus: a case report

The epithalamus region contains the tiny, functionally endocrine pineal gland, which has the shape of a pinecone. Less than 1% of adult primary intracranial malignancies are pineal parenchymal tumors, which are incredibly uncommon brain tumors. A rare variety of pineal parenchymal tumors are those with intermediate differentiation. These tumors, whose namesake refers to a malignant pineal parenchymal tumor, are intermediate between pineoblastomas and pineocytomas (a benign pineal parenchymal tumor).

Case Presentation

A female patient, age 13, who had been experiencing terrible headaches on and off for a month, went to the emergency room. Along with the headache, she experienced nausea, vomiting, dizziness, and blurred eyesight. A nonenhanced computed tomography scan was used for the initial brain neuroimaging, which showed a hypodense mass posterior to the midbrain and superior to the cerebellum. A heterogeneous bulk was visible on MRI.

Clinical Outcome

The headache, vertigo, visual disturbance, nausea, and vomiting have all improved, according to the patient. Both postoperative MRIs with and without contrast revealed the resolution of the obstructive hydrocephalus and the absence of any residual enhancing mass. The patient was followed up for 2 months without any complications or adverse events.

Conclusion

One should carefully investigate a headache as the early symptom of many illnesses and rule out any other potential causes. This would therefore enable us to create a management structure for such a very unusual malignancy.

Treatment of Pineal Region Rosette-Forming Glioneuronal Tumors (RGNT)

Simple Summary

The WHO classification of tumors of the central nervous system described for the first time the extremely rare entity of rosette-forming glioneuronal tumors (RGNT, CNS WHO grade 1) in 2007. Due to the rarity of this entity in the pineal region, no specific therapy guidelines currently exist. With our large cohort of patients treated at a single center (from August 2018–June 2021) and with the already described cases in the literature, we would like to highlight possible therapy and follow-up concepts. After the main symptoms of headache or generalized epileptic seizure, cystic lesions adjacent to the pineal gland and the third ventricle were diagnosed in imaging. None of the patients underwent additional chemotherapy or radiotherapy after gross total (GTR)/subtotal resection or endoscopic biopsy. In cases where surgical resection seems feasible with a reasonable surgical risk, we advocate GTR. Long-term MRI follow-up is essential to detect a slow tumor progression.

Abstract

Background: Rosette-forming glioneuronal tumor (RGNT) is an extremely rare entity described for the first time in the WHO classification of tumors of the central nervous system in 2007. Predominantly, single case reports of RGNT in the pineal region have been published, and specific therapy concepts are pending. Methods: The study group comprised all patients with the RGNT (CNS WHO grade 1) in the pineal region that underwent microsurgical tumor removal in our center (August 2018–June 2021). Surgical strategy, histological findings, and clinical outcome are presented, and the results are evaluated and compared to published case reports. Results: Four male patients aged under 50 years (range between 20 and 48 years) and one female patient, 51 years old, were included in this study. Chronic headaches and generalized epileptic seizures were the main symptoms. Supra-cerebellar infratentorial gross total tumor resection (GTR) was performed in two cases, two patients underwent subtotal tumor resection, and an endoscopic biopsy was performed in case five. Conclusion: In cases where surgical resection seems feasible with a reasonable surgical risk, we advocate GTR. Regular and long-term MRI follow-up is essential to detect a slow tumor progression. The role of additional chemotherapy or radiotherapy remains unclear.

Molecular analyses of rosette-forming glioneuronal tumor of the midbrain tegmentum: A report of two cases and a review of the FGFR1 status in unusual tumor locations

Background:

Rosette-forming glioneuronal tumor (RGNT) is a rare tumor that arises primarily in the posterior fossa, with molecular features of FGFR1 mutation. A previous study reported that brainstem RGNT accounts for only 2.7% cases; therefore, midbrain RGNT is infrequent.

Case Description:

The authors encountered two cases of RGNT located in the midbrain tegmentum (Case 1: 23-year-old woman and Case 2: 18-year-old boy), both exhibiting similar cystic components with gadolinium-enhanced cyst walls on preoperative magnetic resonance imaging, surgically resected through the occipital transtentorial approach. Histological findings in both cases comprised two characteristic architectures of neurocytic and glial components, typical of RGNT. Molecular assessment revealed no FGFR1 mutation in the initial specimen, but revealed FGFR1 K656E mutation in the recurrent specimen in Case 1 and showed no FGFR1 mutation but showed TERT C228T mutation in Case 2. Neither case revealed IDH1/2, BRAF, H3F3A K27, H3F3A G34, or HIST1H3B K27 mutations. DNA methylation-based classification (molecularneuropathology.org) categorized both cases as RGNT, whose calibrated scores were 0.99 and 0.47 in Cases 1 and 2, respectively.

Conclusion:

Midbrain tegmentum RGNTs exhibited typical histological features but varied FGFR1 statuses with TERT mutation. RGNT in rare locations may carry different molecular alterations than those in other common locations, such as the posterior fossa.

Rosette-Forming Glioneuronal Tumor at Septum Pellucidum: Insights Gained from a Common Tumor at Rare Location

The rosette-forming glioneuronal tumor (RGNT) is an uncommon entity and carries a special character because of its mixed glial and neuronal composition in the histomorphological appearance. These lesions have a benign character and carry a good outcome if undergoes gross total resection. Over the past 15 years, there have been a significant change in their nomenclature depending upon the location to histological composition. Herein, we report an interesting case of a 26-year-old lady who was diagnosed to have the lesion at the septum pellucidum with significant symptoms in the form of headache and seizure episodes. A gross total resection was achieved and she made an uneventful recovery. We discuss the literature on the incidence, location, and histological characteristics of the RGNT in various age groups.

Rosette-Forming Glioneuronal Tumor in the Pineal Region: A Series of 6 Cases and Literature Review

Resected lesions from the pineal region are rare specimens encountered by surgical pathologists, and their heterogeneity can pose significant diagnostic challenges. Here, we reviewed 221 pineal region lesions resected at New York-Presbyterian Hospital/Columbia University Irving Medical Center from 1994 to 2019 and found the most common entities to be pineal parenchymal tumors (25.3%), glial neoplasms (18.6%), and germ cell tumors (17.6%) in this predominantly adult cohort of patients. Six cases of a rare midline entity usually found exclusively in the fourth ventricle, the rosette-forming glioneuronal tumor, were identified. These tumors exhibit biphasic morphology, with a component resembling pilocytic astrocytoma admixed with variable numbers of small cells forming compact rosettes and perivascular pseudorosettes. Targeted sequencing revealed a 100% co-occurrence of novel and previously described genetic alterations in the mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) signaling pathways, suggesting a synergistic role in tumor formation. The most common recurrent mutation, PIK3CA H1047R, was identified in tumor cells forming rosettes and perivascular pseudorosettes. A review of the literature revealed 16 additional cases of rosette-forming glioneuronal tumors in the pineal region. Although rare, this distinctive low-grade tumor warrants consideration in the differential diagnosis of pineal region lesions.

Pineal region tumors: pathophysiological mechanisms of presenting symptoms

Pineal region tumors (PRTs) affect all ages, with a remarkable proportion of cases occurring in children. They are mainly classified into three categories, namely germ cell tumors (GCTs), pineal parenchymal tumors (PPTs), and other tumors such as gliomas and tumors of the surrounding structures. The purpose of this article is to review the current literature regarding pathophysiological mechanisms of the presenting clinical features of patients with PRT. The usual presentation of PRTs is the symptoms of obstructive hydrocephalus and intracranial hypertension, such as headache and vomiting. However, there is a remarkable spectrum of clinical findings that can be caused by such lesions. These include ophthalmologic and endocrinologic disturbances, motor and sensory abnormalities, and cognitive and psychiatric symptoms. The unique anatomic location of the pineal gland, which is close to many vital brain structures, is crucial for the explanation of most of those findings. In rare cases, manifestations of intracranial bleeding may be the presenting feature of a PRT. Tumor histology and patient's age can affect the clinical presentation. Hydrocephalus is the most common clinical syndrome of a PRT because of the location of the pineal gland. Presenting symptoms also include ophthalmologic, endocrinologic, motor, sensory, cognitive, and psychiatric symptoms. Clinicians should be aware of the initial symptoms of PRTs, including the misleading ones, in order to avoid delay in the diagnosis and management of these life-threatening lesions.

Rosette-forming glioneuronal tumor of the fourth ventricle; A case report and review of the literature

Despite mostly indolent course and favorable postoperative outcome long-term follow-up studies are needed to identify the most appropriate therapeutic strategies to minimize surgical morbidity and neurologic injury in patients with RGNT.

A case of a rosette-forming glioneuronal tumor with clinicopathological features of a dysembryoplastic neuroepithelial tumor and fibroblast growth factor receptor 1 internal tandem duplication

Rosette-forming glioneuronal tumors (RGNTs) are benign WHO grade 1 tumors that occur in the ventricular system, particularly the fourth ventricle. RGNTs and dysembryoplastic neuroepithelial tumors (DNTs) are both categorized as neuronal and mixed neuronal-glial tumors and may be difficult to distinguish. Coexistence of the two tumor types has been reported. Here, we report a pediatric case of RGNT with DNT-like features showing intraventricular dissemination. The tumor occurred in the medial temporal lobe and presented with specific pathological glioneuronal elements including floating neurons, which are typical in DNTs, but was diagnosed as RGNT because of the presence of neurocytic rosettes. Genetic analysis detected fibroblast growth factor receptor 1 internal tandem duplication (FGFR1-ITD) of the tyrosine kinase domain, which was previously reported to be specific for DNT. RGNTs with FGFR1-ITD may show atypical clinical presentation and pathological features.

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.

Supratentorial intraventricular rosette-forming glioneuronal tumors - Case report and review of treatment paradigms

Background

Rosette-forming glioneuronal tumors (RGNT) are slow-growing WHO Grade I tumors that are characterized by mixed histology and rosette formation. Although typically located in the posterior fossa, these tumors can rarely originate elsewhere. Here, we describe the fourth case in literature where an RGNT was localized to the lateral ventricles and detail the treatment approach.

Case Description

A 41-year-old male presented with a 10 day history of gradually worsening headaches and mild gait difficulty. Computed tomography and magnetic resonance imaging (MRI) identified a heterogeneously enhancing 6.0 cm left lateral ventricular cystic mass with hydrocephalus. An interhemispheric transcallosal approach was performed for tumor debulking. The mass was emanating from the roof of the left lateral ventricle. Sub-total resection (STR) was achieved. Pathology showed a glioneuronal neoplasm with vague neurocytic rosettes and loose perivascular pseudorosettes. Tumor vessels were thickly hyalinized and contained eosinophilic granular bodies and Rosenthal fibers. Tumor stained positive for GFAP, S-100, OLIG2, and SOX10, and patchy positive for epithelial membrane antigen (EMA), D2-40, CD99, and p16. Neurocytic rosettes and perivascular structures stained positive for synaptophysin. The patient was discharged home uneventfully and remained intact at his 6-month follow-up visit. Long-term care included MRI surveillance with repeat surgery being considered in case of progression.

Conclusion

In this report, we describe the fourth case of an RGNT being isolated to the lateral ventricles and the first where it stained positive for EMA and D2-40. Our patient's uneventful recovery after STR indicates that surgery alone continues to be a viable initial treatment option.

Malignant Transformation of a Rosette-Forming Glioneuronal Tumor to Glioblastoma

BACKGROUND

A rosette-forming glioneuronal tumor (RGNT), a rare brain tumor, presents as a benign feature with a favorable outcome. To date, a few cases with aggressive behaviors, such as recurrence or dissemination, but none with malignant transformation, have been reported. We describe 1 case that recurred as glioblastoma after complete resection of the benign RGNT.

CASE DESCRIPTION

A man aged 58 years presented with headache and dizziness without neurologic symptoms. Magnetic resonance imaging showed a 4 × 2.5 cm, well-demarcated mass in the left cerebellar hemisphere. The patient underwent gross total resection of the tumor and a diagnosis of RGNT was made. There was no evidence of recurrence on serial follow-up. However, a recurrent heterogeneous enhancing mass in the previous surgical cavity was observed on a 7-year postoperative magnetic resonance imaging scan. Reoperation was performed and a histopathological study revealed a glioblastoma.

CONCLUSIONS

To the best of our knowledge, this is the first case of spontaneous malignant transformation of an RGNT. Our case may be helpful in better understanding the biological behavior and clinical outcome of RGNT. We emphasize the malignant potential of this rare tumor and the necessity of future large-scaled research for most appropriate therapeutic strategies.

Iodine promotes thyroid cancer development via SPANXA1 through the PI3K/AKT signalling pathway

The aim of this study was to examine the impact of iodine on the development of thyroid cancer cells and to detect the underlying mechanisms. It was observed that proliferation was promoted and apoptosis was inhibited in cells treated with iodine at a specific concentration. This treatment group was then selected for further analysis, to investigate how iodine affects the development of thyroid cancer cells. It was reported that sperm protein associated with the nucleus, X-linked, family member A1 (SPANXA1) expression in iodine-treated cells was significantly upregulated. Furthermore, downregulation of SPANXA1 inhibited cell proliferation, migration and invasion, and promoted cell apoptosis. These results suggested that SPANXA1 played an important role in iodine-treated thyroid cancer cells. Novel associations between SPANXA1 and thyroid cancer were described in the current study. In addition, SPANXA1 gene silencing resulted in the downregulation of PI3K and phosphorylated (p)AKT expression in iodine-treated thyroid cancer cells, whereas iodine treatment alone resulted in upregulated PI3K and p-AKT expression. Inhibiting PI3K further suppressed cell proliferation and contributed to apoptosis, even in the presence of SPANXA1 at high levels. As a consequence, PI3K/AKT may be one of the key signalling pathways by which iodine promotes thyroid cancer development in association with SPANXA1. In addition, our results further suggested that patients with thyroid cancer may need to avoid high-iodine intake.

Malignant Transformation of a Rosette-Forming Glioneuronal Tumor with IDH1 Mutation: A Case Report and Literature Review

Background

Rosette-forming glioneuronal tumor (World Health Organization grade I) is considered as a benign tumor with very low potential for progression. The potential for malignant transformation of this tumor is not known and has never been reported before in literature.

Case Description

We report a 42-year-old man, diagnosed with rosette-forming glioneuronal tumor of the fourth ventricle with a positive isocitrate dehydrogenase 1 mutation, progressed to glioblastoma after 6 years from diagnosis. We discuss the clinical history, radiological findings, and histopathological characteristic with immunohistochemistry findings observed in this unique case.

Conclusions

Despite being acceptable as benign, based on our observations in this case, there is a potential for malignant transformation of rosette-forming glioneuronal tumor. The role of isocitrate dehydrogenase 1 mutation leading to malignant transformation could not be established as our finding is novel and further prospective studies are required to prove this association.

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.

Remote intracranial recurrence of IDH mutant gliomas is associated with TP53 mutations and an 8q gain

Most IDH mutant gliomas harbor either 1p/19q co-deletions or TP53 mutation; 1p/19q co-deleted tumors have significantly better prognoses than tumors harboring TP53 mutations. To investigate the clinical factors that contribute to differences in tumor progression of IDH mutant gliomas, we classified recurrent tumor patterns based on MRI and correlated these patterns with their genomic characterization. Accordingly, in IDH mutant gliomas (N = 66), 1p/19 co-deleted gliomas only recurred locally, whereas TP53 mutant gliomas recurred both locally and in remote intracranial regions. In addition, diffuse tensor imaging suggested that remote intracranial recurrence in the astrocytomas, IDH-mutant with TP53 mutations may occur along major fiber bundles. Remotely recurrent tumors resulted in a higher mortality and significantly harbored an 8q gain; astrocytomas with an 8q gain resulted in significantly shorter overall survival than those without an 8q gain. OncoScan^® arrays and next-generation sequencing revealed specific 8q regions (i.e., between 8q22 and 8q24) show a high copy number. In conclusion, only tumors with TP53 mutations showed patterns of remote recurrence in IDH mutant gliomas. Furthermore, an 8q gain was significantly associated with remote intracranial recurrence and can be considered a poor prognostic factor in astrocytomas, IDH-mutant.

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.

Comprehensive genetic characterization of rosette-forming glioneuronal tumors: independent component analysis by tissue microdissection

A rosette-forming glioneuronal tumor (RGNT) is a rare mixed neuronal-glial tumor characterized by biphasic architecture of glial and neurocytic components. The number of reports of genetic analyses of RGNTs is few. Additionally, the genetic background of the unique biphasic pathological characteristics of such mixed neuronal-glial tumors remains unclear. To clarify the genetic background of RGNTs, we performed separate comprehensive genetic analyses of glial and neurocytic components of five RGNTs, by tissue microdissection. Two missense mutations in FGFR1 in both components of two cases, and one mutation in PIK3CA in both components of one case, were detected. In the latter case with PIK3CA mutation, the additional FGFR1 mutation was detected only in the glial component. Moreover, the loss of chromosome 13q in only the neurocytic component was observed in one other case. Their results suggested that RGNTs, which are tumors harboring two divergent differentiations that arose from a single clone, have a diverse genetic background. Although previous studies have suggested that RGNTs and pilocytic astrocytomas (PAs) represent the same tumor entity, their results confirm that the genetic background of RGNTs is not identical to that of PA.

Rosette-forming Glioneuronal Tumor: A Rare Posterior Fossa Tumor in an Adolescent

Rosette-forming glioneuronal tumor (RGNT) is a rare variety of slow growing mixed glioneuronal tumor involving primarily fourth ventricular region and occurring predominantly in young adults. We present a case of a 16-year-old boy who presented with dizziness and occipital headache. On radiological evaluation, a fairly large hypodense posterior fossa mass lesion in relation to the left side of the vermis, with a large cystic component was found. Surgical resection of the tumor was performed. Histopathological examination showed a biphasic tumor composed of bland neurocytic cells, arranged in the form of neurocytic rosettes along with glial areas resembling low-grade glioma. The neurocytic rich region shows strong synaptophysin positivity in the neuropil-rich core of the rosettes. Methylation-inhibited binding proliferative index was low (<1%). Based on these features, a diagnosis of RGNT was made. RGNT of the fourth ventricle should be considered in differential diagnosis of posterior fossa lesions, especially in relation to fourth ventricle and vermis in young adults.

Low-grade epilepsy-associated neuroepithelial tumours - the 2016 WHO classification

Rapid developments in molecular genetic technology and research have swiftly advanced our understanding of neuro-oncology. As a consequence, the WHO invited their expert panels to revise the current classification system of brain tumours and to introduce, for the first time, a molecular genetic approach for selected tumour entities, thus setting a new gold standard in histopathology. The revised 5th edition of the 'blue book' was released in May 2016 and will have a major impact in stratifying diagnosis and treatment. However, low-grade neuroepithelial tumours that present with early-onset focal epilepsy and are mostly seen in children and young adults (previously designated as long-term epilepsy-associated neuroepithelial tumours, LEAT) lack such innovative clinicopathological and molecular genetic tools. The Neuropathology Task Force of the International League against Epilepsy will critically discuss this issue, and will offer perspectives on how to decipher and validate clinically meaningful LEAT entities using the current WHO approach that integrates clinicopathological and genetic classification systems.

Prediction of genetic subgroups in adult supra tentorial gliomas by pre- and intraoperative parameters

Recent progress in neuro-oncology has validated the significance of genetic diagnosis in gliomas. We previously investigated IDH1/2 and TP53 mutations via Sanger sequencing for adult supratentorial gliomas and reported that PCR-based sequence analysis classified gliomas into three genetic subgroups that have a strong association with patient prognosis: IDH mutant gliomas without TP53 mutations, IDH and TP53 mutant gliomas, and IDH wild-type gliomas. Furthermore, this analysis had a strong association with patient prognosis. To predict genetic subgroups prior to initial surgery, we retrospectively investigated preoperative radiological data using CT and MRI, including MR spectroscopy (MRS), and evaluated positive 5-aminolevulinic acid (5-ALA) fluorescence as an intraoperative factor. We subsequently compared these factors to differentiate each genetic subgroup. Multiple factors such as age at diagnosis, tumor location, gadolinium enhancement, 5-ALA fluorescence, and several tumor metabolites according to MRS, such as myo-inositol (myo-inositol/total choline) or lipid20, were statistically significant factors for differentiating IDH mutant and wild-type, suggesting that these two subtypes have totally distinct characteristics. In contrast, only calcification, laterality, and lipid13 (lipid13/total Choline) were statistically significant parameters for differentiating TP53 wild-type and mutant in IDH mutant gliomas. In this study, we detected several pre- and intraoperative factors that enabled us to predict genetic subgroups for adult supratentorial gliomas and clarified that lipid13 quantified by MRS is the key tumor metabolite that differentiates TP53 wild-type and mutant in IDH mutant gliomas. These results suggested that each genetic subtype in gliomas selects the distinct lipid synthesis pathways in the process of tumorigenesis.

PIK3CA mutation in a mixed dysembryoplastic neuroepithelial tumor and rosette forming glioneuronal tumor, a case report and literature review

BACKGROUND

Rosette forming glioneuronal tumors are rare, World Health Organization (WHO) grade I novel tumors frequently affecting the fourth ventricle or posterior fossa with typical neuronal pseudorosettes. RGNTs have been described as possessing additional histologic features of DNETs or pilocytic astrocytomas. Activating PIK3CA mutations have been identified as recurring genetic event in RGNTs.

METHODS

We report a 35year old man who presented with binocular diplopia, headache, and was found to have a third ventricle tumor. Tumor pathology and oncogene evaluation were conducted.

RESULTS

The tumor demonstrated histologic features consistent with mixed RGNT/DNET. Genetic studies revealed a PIK3CA mutation in exon 9 (E545K, C. 1633G>A) without IDH1, p53, 1p19q chromosomal co-deletion, or BRAF mutations. A literature search revealed six cases of PIK3CA mutations in RGNTs and seven cases of mixed RGNT/DNET. No cases of mixed RGNT/DNET with a PIK3CA mutation have been described.

CONCLUSION

This is the first documented case of an RGNT/DNET with an activating PIK3CA mutation. The presence of a PIK3CA mutation aids histologic classification in the setting of mixed histology, and may have implications for targeting the PI3K/AKT/mTOR pathway in this tumor type.

Integrated tumor and germline whole-exome sequencing identifies mutations in MAPK and PI3K pathway genes in an adolescent with rosette-forming glioneuronal tumor of the fourth ventricle

The integration of genome-scale studies such as whole-exome sequencing (WES) into the clinical care of children with cancer has the potential to provide insight into the genetic basis of an individual's cancer with implications for clinical management. This report describes the results of clinical tumor and germline WES for a patient with a rare tumor diagnosis, rosette-forming glioneuronal tumor of the fourth ventricle (RGNT). Three pathogenic gene alterations with implications for clinical care were identified: somatic activating hotspot mutations in FGFR1 (p.N546K) and PIK3CA (p.H1047R) and a germline pathogenic variant in PTPN11 (p.N308S) diagnostic for Noonan syndrome. The molecular landscape of RGNT is not well-described, but these data are consistent with prior observations regarding the importance of the interconnected MAPK and PI3K/AKT/mTOR signaling pathways in this rare tumor. The co-occurrence of FGFR1, PIK3CA, and PTPN11 alterations provides further evidence for consideration of RGNT as a distinct molecular entity from pediatric low-grade gliomas and suggests potential therapeutic strategies for this patient in the event of tumor recurrence as novel agents targeting these pathways enter pediatric clinical trials. Although RGNT has not been definitively linked with cancer predisposition syndromes, two prior cases have been reported in patients with RASopathies (Noonan syndrome and neurofibromatosis type 1 [NF1]), providing an additional link between these tumors and the mitogen-activated protein kinase (MAPK) signaling pathway. In summary, this case provides an example of the potential for genome-scale sequencing technologies to provide insight into the biology of rare tumors and yield both tumor and germline results of potential relevance to patient care.

Rosette-forming Glioneuronal Tumors in the Posterior Third Ventricle

Rosette-forming glioneuronal tumor (RGNT) is a rare brain tumor found almost exclusively within the fourth ventricle. These grade I tumors were first included in the World Health Organization (WHO) Classification for the central nervous system in 20071. Since then, approximately 49 cases have been published.

There are no reported cases of RGNT within the third ventricle, although this tumor has also been described in the pineal region, the tectum and within the aqueduct. Supratentorial localization is quite rare, with only three published: one was found in the septum pellucidum, another within the optic nerve in neurofibromatosis type 1 (NF1) patient and one in a patient with multiple RGNT in the lateral ventricle. The authors report the first case series in the literature of RGNT occurring within the posterior third ventricle.

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.

Thalamic rosette-forming a glioneuronal tumor in an elderly patient: Case report and literature review

The rosette-forming glioneuronal tumor (RGNT) is a novel type of brain tumor recently listed in the WHO 2007 classification of central nervous system (CNS) tumors. We report the case of a 75-year-old woman harboring a thalamic RGNT with third ventricle dissemination. Age and location make the present case exceptional and which has never previously been reported. A review of the clinical, pathological and radiological features is presented along with the relevant literature.

Rosette-forming glioneuronal tumor of the fourth ventricle

We present a case of a 22-year-old asymptomatic female whose CT study (performed following trauma) incidentally discovered a posterior fossa mass. The lesion was further evaluated with a MRI study, and (following discussion with the patient and her family) elective surgical resection of the lesion was performed. On pathology, histological evaluation revealed a diagnosis of rosette-forming glioneuronal tumor of the fourth ventricle. RGNT of the fourth ventricle or posterior fossa should always be considered in the differential diagnosis of infratentorial lesions, especially in young adults.

PCR-Based Simple Subgrouping Is Validated for Classification of Gliomas and Defines Negative Prognostic Copy Number Aberrations in IDH Mutant Gliomas

Genetic subgrouping of gliomas has been emphasized recently, particularly after the finding of isocitrate dehydrogenase 1 (IDH1) mutations. In a previous study, we investigated whole-chromosome copy number aberrations (CNAs) of gliomas and have described genetic subgrouping based on CNAs and IDH1 mutations. Subsequently, we classified gliomas using simple polymerase chain reaction (PCR)-based methods to improve the availability of genetic subgrouping. We selected IDH1/2 and TP53 as markers and analyzed 237 adult supratentorial gliomas using Sanger sequencing. Using these markers, we classified gliomas into three subgroups that were strongly associated with patient prognoses. These included IDH mutant gliomas without TP53 mutations, IDH mutant gliomas with TP53 mutations, and IDH wild-type gliomas. IDH mutant gliomas without TP53 mutations, which mostly corresponded to gliomas carrying 1p19q co-deletions, showed lower recurrence rates than the other 2 groups. In the other high-recurrence groups, the median progression-free survival (PFS) and overall survival (OS) of patients with IDH mutant gliomas with TP53 mutations were significantly longer than those of patients with IDH wild-type gliomas. Notably, most IDH mutant gliomas with TP53 mutations had at least one of the CNAs +7q, +8q, −9p, and −11p. Moreover, IDH mutant gliomas with at least one of these CNAs had a significantly worse prognosis than did other IDH mutant gliomas. PCR-based mutation analyses of IDH and TP53 were sufficient for simple genetic diagnosis of glioma that were strongly associated with prognosis of patients and enabled us to detect negative CNAs in IDH mutant gliomas.

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.

Rosette forming glioneuronal tumor of the fourth ventricle in squash cytology smear

Rosette forming glioneuronal tumor (RGNT) is a recently recognized and extremely rare glioneuronal tumor occurring in the fourth ventricle. It is crucial for the cytopathologist to be aware of this entity as it can be easily mistaken for more common neoplasms occurring at this site. We present here the cytology of such a rare case of RGNT that was misdiagnosed as ependymoma. The varying cytological features of this entity, as well as the common diagnostic difficulties encountered in cytology, are highlighted in this report.

Rare pathologies in the posterior third ventricular region in children: case series and review

Tumors of the pineal region in children often belong to 2 categories, namely germ cell tumors and pineal parenchymal tumors. Very rare pathologies have previously been reported in this region. Most of these tumors may be similar radiologically, while their management differs. The present series reports 2 children with pineal region tumors, each one being a rare pathological entity by itself, namely an embryonal tumor with abundant neuropil and true rosettes (ETANTR) and a rosette-forming glioneuronal tumor (RGNT). Very few such cases in each pathology have been reported in the literature for the pediatric age group up to now. Our series consists of 2 children, both presenting with a raised intracranial pressure of short duration. Imaging revealed lesions in the pineal region with similar radiological features. Both ETANTR and RGNT demonstrated mild enhancement. The 2 patients underwent surgical decompression either by Poppen's approach (n = 1) or a supracerebellar infratentorial approach (n = 1). The patient with ETANTR was advised radiotherapy, while the child with RGNT was advised a regular follow-up. This series presents some rare pathologies which can occur in the posterior third ventricular region with similar radiological features. Management differs based on the histology of the case.

Pineal region masses--imaging findings and surgical approaches

The anatomy of the pineal region is complex. Despite advances in surgical techniques since the first reported successful pineal region surgery in the early 20th century, pineal region surgery remains challenging owing to the proximity of deep cerebral veins and dorsal midbrain structures critical for vision. In this article, we review the relevant surgical anatomy of the pineal region and discuss historically important and current surgical approaches. We describe specific imaging features of pineal region masses that may affect surgical planning and review neoplastic and nonneoplastic masses that occur in the pineal region.

An individual patient data meta-analysis on characteristics and outcome of patients with papillary glioneuronal tumor, rosette glioneuronal tumor with neuropil-like islands and rosette forming glioneuronal tumor of the fourth ventricle

Background and Purpose

In 2007, the WHO classification of brain tumors was extended by three new entities of glioneuronal tumors: papillary glioneuronal tumor (PGNT), rosette-forming glioneuronal tumor of the fourth ventricle (RGNT) and glioneuronal tumor with neuropil-like islands (GNTNI). Focusing on clinical characteristics and outcome, the authors performed a comprehensive individual patient data (IPD) meta-analysis of the cases reported in literature until December 2012.

Methods

PubMed, Embase and Web of Science were searched for peer-reviewed articles reporting on PGNT, RGNT, and GNTNI using predefined keywords.

Results

95 publications reported on 182 patients (PGNT, 71; GNTNI, 26; RGNT, 85). Median age at diagnosis was 23 years (range 4–75) for PGNT, 27 years (range 6–79) for RGNT, and 40 years (range 2–65) for GNTNI. Ninety-seven percent of PGNT and 69% of GNTNI were located in the supratentorial region, 23% of GNTNI were in the spinal cord, and 80% of RGNT were localized in the posterior fossa. Complete resection was reported in 52 PGNT (73%), 36 RGNT (42%), and 7 GNTNI (27%) patients. Eight PGNT, 3 RGNT, and 12 GNTNI patients were treated with chemo- and/or radiotherapy as the primary postoperative treatment. Follow-up data were available for 132 cases. After a median follow-up time of 1.5 years (range 0.2–25) across all patients, 1.5-year progression-free survival rates were 52±12% for GNTNI, 86±5% for PGNT, and 100% for RGNT. The 1.5-year overall-survival were 95±5%, 98±2%, and 100%, respectively.

Conclusions

The clinical understanding of the three new entities of glioneuronal tumors, PGNT, RGNT and GNTNI, is currently emerging. The present meta-analysis will hopefully contribute to a delineation of their diagnostic, therapeutic, and prognostic profiles. However, the available data do not provide a solid basis to define the optimum treatment approach. Hence, a central register should be established.

A peculiar histopathological form of dysembryoplastic neuroepithelial tumor with separated pilocytic astrocytoma and rosette-forming glioneuronal tumor components

Dysembryoplastic neuroepithelial tumors (DNTs) mostly display typical clinical, neuroimaging and histopathological features, but sometimes they reveal heterogeneous or non-specific morphology, which results in diagnostic dilemmas. We present a case of a young adult with longstanding, intractable epilepsy associated with a multinodular cystic lesion in the temporal lobe. The lesion consisted of morphologically different components. In particular, a few cortical nodules displayed a specific glioneuronal element with floating neurons typically found in DNT. Two large, well-circumscribed nodules were entirely composed of biphasic, piloid, astroglial patterns that corresponded strictly to a pilocytic astrocytoma. The well-defined areas, which contained numerous distinct neurocytic-like rosettes, were identical with rosette-forming glioneuronal tumors (RGNTs). This type of neurocytic rosette was widespread within the surrounding piloid background. Some solid nodules exhibited increased cellularity, oligodendroglioma-like elements and a focal ribbon cell arrangement. The lesion was associated with advanced reactive gliosis and foci of dysplastic changes in the adjacent cortex. The clinico-radiological and main histopathological features were consistent with a diagnosis of a complex variant of DNT composed of pilocytic and rosette-forming glioneuronal components. Although both piloid tissue and rosette-like formations have been occasionally mentioned in DNT lesions, the present case of DNT was unique in its well-circumscribed, separate pilocytic and RGNT nodules. We concluded that it represented an unusual, mixed pilocytic/RGNT variant of DNT.

Rosette-forming glioneuronal tumor of the fourth ventricle with neurocytoma component

Rosette-forming glioneuronal tumor (RGNT) was first published in 2002 and was described as a benign and indolent tumor. It was also included in the 2007 World Health Organization (WHO) classification of tumors as a grade 1 tumor for its benign clinical behavior and the possibility of surgical cure. Pathologically, RGNT is a mixed neuronal-glial tumor which consists of two distinct histological components-one with uniform neurocytes forming rosettes and/or perivascular pseudorosettes and the other being astrocytic in nature resembling pilocytic astrocytoma (biphasic pattern). We present the clinical course and pathological findings of two distinctively different cases. The first one was a 4-year-old girl with head trauma and a tumor which was incidentally found by CT. Pathology revealed that the tumor contained neurocytoma components and areas of relatively high proliferative ability with the first report of the presence of midsized bright elliptic cells. The other case was a 19-year-old girl whose imaging studies showed hydrocephalus and a brain stem tumor. She underwent endoscopic third ventriculostomy and biopsy, followed by observation. An MRI taken 6 months later showed progression of the tumor and she subsequently had the tumor excised. We are considering the possibility for our RGNT cases to correspond to a higher WHO grade as they have shown rapid progression, contrary to the already established, and their character, origin, differential diagnosis, and treatment plans have been discussed.

IDH1/2 mutations target a key hallmark of cancer by deregulating cellular metabolism in glioma

Isocitrate dehydrogenase (IDH) enzymes have recently become a focal point for research aimed at understanding the biology of glioma. IDH1 and IDH2 are mutated in 50%-80% of astrocytomas, oligodendrogliomas, oligoastrocytomas, and secondary glioblastomas but are seldom mutated in primary glioblastomas. Gliomas with IDH1/2 mutations always harbor other molecular aberrations, such as TP53 mutation or 1p/19q loss. IDH1 and IDH2 mutations may serve as prognostic factors because patients with an IDH-mutated glioma survive significantly longer than those with an IDH-wild-type tumor. However, the molecular pathogenic role of IDH1/2 mutations in the development of gliomas is unclear. The production of 2-hydroxyglutarate and enhanced NADP+ levels in tumor cells with mutant IDH1/2 suggest mechanisms through which these mutations contribute to tumorigenesis. Elucidating the pathogenesis of IDH mutations will improve understanding of the molecular mechanisms of gliomagenesis and may lead to development of a new molecular classification system and novel therapies.

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

INTRODUCTION

Rosette-forming glioneuronal tumour of the fourth ventricle is a rarely described entity. While usually having an indolent course and hence classified as a WHO grade 1 tumour, the precise characteristics and risk of recurrence of this tumour are still unknown. In addition, the preferred treatment modality remains unclear.

DISCUSSION

We present a case of an 8-year old with an early recurrence of 9 months after undergoing a sub-total resection of her tumour. Following further resection, there was no tumour present on the 3-month follow-up. In order to better characterise this tumour entity, we performed a review of the available literature on the subject. We found that it mainly affected young adults and had a female predominance. While initially these tumours were described in the fourth ventricle, the current literature suggests that they may be found in a larger variety of sites within the brain and spinal cord. There are several reports of recurrence occurring between 9 months and 10 years following surgery. There is as yet no feature of the tumour that appears to predict the risk of recurrence.

CONCLUSION

This phenomenon warrants further examination to discover if there is a sub-section of tumours that is likely to recur, and until this is established, all patients should be followed up at regular intervals.