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Rosette-forming glioneuronal neoplasm — Clinical Guidelines

Overview

Rosette-forming glioneuronal tumor (RGNT) is a rare, low-grade glioneuronal neoplasm primarily affecting young adults, with a predilection for the fourth ventricle but also observed in other brain regions such as the cerebellum, brain stem, and thalamus 1 2 6 10. These tumors are characterized by the presence of rosette-like structures composed of neurocytic cells embedded in an astrocytic background. Clinically significant due to their indolent yet potentially progressive nature, RGNTs can present with nonspecific symptoms like headache, nausea, and behavioral changes, necessitating careful monitoring and timely intervention to prevent complications such as hydrocephalus and mass effect 1 3 13. Understanding RGNT is crucial in day-to-day practice for accurate diagnosis and appropriate management, particularly in distinguishing it from more common or more aggressive lesions 1 2.

Pathophysiology

The pathophysiology of RGNT involves complex interactions between glial and neuronal elements, suggesting a dual origin from progenitor cells with both astrocytic and neuronal differentiation potential 5 8. Molecularly, these tumors often harbor mutations in genes such as FGFR1, with recurrent co-mutations in PIK3CA and NF1, indicating dysregulation in signaling pathways critical for cell proliferation and differentiation 5 7. The presence of specific epigenetic profiles further supports the unique molecular signature of RGNTs, distinguishing them from other glioneuronal tumors like dysembryoplastic neuroepithelial tumors (DNTs) 2 5. Despite their histological resemblance to pilocytic astrocytomas, RGNTs lack common genetic alterations such as KIAA1549-BRAF fusions, highlighting their distinct biological behavior 11. These molecular and cellular mechanisms underpin the tumor's growth pattern, which can be indolent yet variable, necessitating individualized clinical management 5 8.

Epidemiology

RGNTs are exceedingly rare, with most reported cases being individual case studies or small series, making precise incidence and prevalence figures challenging to establish 1 2 9. Typically, these tumors affect young adults, with a mean age of onset around 23 years, and there is a slight female predominance observed in some reports 2 6. Geographic distribution does not appear to show significant regional clustering based on current literature, suggesting a sporadic occurrence rather than environmental influences 1 2. Over time, the recognition and reporting of RGNTs have increased, reflecting improved diagnostic capabilities and awareness among clinicians, though large-scale epidemiological studies are lacking 9.

Clinical Presentation

Patients with RGNT often present with nonspecific symptoms due to the tumor's location and slow growth, including headaches, nausea, vomiting, and cognitive or behavioral changes 1 3 13. More specific neurological deficits can arise depending on the tumor's site, such as cerebellar dysfunction (ataxia, nystagmus) or hydrocephalus symptoms (irritability, lethargy) 1 3. Red-flag features include rapid progression of symptoms, signs of increased intracranial pressure, or unexpected neurological deficits that warrant urgent evaluation 1 3. Early detection through incidental imaging findings is crucial, as these tumors can mimic other conditions like cysticercosis or other posterior fossa lesions, necessitating a thorough diagnostic workup 2 10.

Diagnosis

The diagnosis of RGNT involves a combination of clinical evaluation, advanced neuroimaging, and histopathological analysis. Diagnostic Approach:

Imaging: MRI is essential, showing characteristic cystic-solid masses with heterogeneous enhancement, often located in the fourth ventricle but also in other regions 1 2 3.

Histopathology: Definitive diagnosis relies on surgical biopsy or resection, where characteristic rosette structures are identified, along with immunohistochemical markers such as synaptophysin, GFAP, and MAP2 1 2 3.

Specific Criteria and Tests:

MRI Findings:

- Hyperintense cystic and solid components on T2-weighted images. - Hypointense solid components on T1-weighted images. - Variable gadolinium enhancement patterns.

Histopathological Features:

- Presence of rosettes with neuropil islands. - Positive synaptophysin staining in rosettes. - GFAP positivity in glial areas, MAP2 positivity in neuronal cells. - Negative NeuN staining, positive Olig2 expression.

Molecular Analysis:

- Epigenetic profiling and genetic testing for FGFR1 mutations, PIK3CA, and NF1 co-mutations 5 7.

Differential Diagnosis:

Pilocytic Astrocytoma: Distinguished by absence of KIAA1549-BRAF fusions and characteristic histological features.

Dysembryoplastic Neuroepithelial Tumor (DNT): Typically found in the temporal lobe and lacks the rosette structures.

Cysticercosis: Mimics imaging features but lacks characteristic histopathological rosettes and immunohistochemical profile.

Ganglioglioma: Exhibits ganglion cells and neoplastic glial cells, differing in cellular composition and location 2 10.

Management

Surgical Management:

Primary Approach: Gross-total resection is ideal when feasible, particularly to prevent hydrocephalus and mass effect 1 4 9.

Indications: Symptomatic patients, suspicion of rapid progression, or risk of CSF obstruction.

Considerations: Careful planning to avoid damage to critical structures due to tumor location.

Post-Surgical Care:

Monitoring: Regular MRI follow-ups to assess for recurrence or progression.

Symptom Management: Address postoperative complications such as mutism with appropriate interventions like bromocriptine 13.

Adjuvant Therapy:

Radiation Therapy: Considered for inoperable or recurrent cases, though evidence is limited and primarily based on expert opinion 4.

Chemotherapy: Not typically indicated due to the low-grade nature of RGNTs, but may be explored in refractory cases 1 9.

Contraindications:

Surgical: Patients with significant comorbidities precluding surgery.

Radiation: Young age and proximity to critical structures limiting radiation feasibility.

Complications

Acute Complications:

Postoperative: Cerebellar mutism, hydrocephalus, infection, and neurological deficits related to surgical manipulation.

Management Triggers: Immediate postoperative monitoring, prompt intervention for signs of increased ICP or infection.

Long-Term Complications:

Recurrence: Regular imaging follow-up to detect early recurrence.

Neurological Decline: Progressive symptoms requiring reassessment and potential re-intervention.

Referral Indicators: Persistent or worsening neurological symptoms, imaging evidence of tumor regrowth.

Prognosis & Follow-up

The prognosis for RGNT is generally favorable, with many patients experiencing stable disease post-resection 1 9. Prognostic indicators include extent of resection, absence of residual tumor, and molecular profiles such as specific FGFR1 mutations 5 7. Recommended follow-up intervals typically involve MRI scans every 6 to 12 months initially, tapering based on stability 1 9. Long-term monitoring is crucial to detect any recurrence early and manage complications effectively.

Special Populations

Pediatrics: RGNTs can occur in children, requiring careful surgical planning to minimize neurological impact 8. Elderly: Rare but possible; management focuses on minimizing surgical risks and optimizing postoperative care 1. Comorbidities: Patients with significant comorbidities may require tailored surgical approaches and intensified postoperative care 1 13. Ethnic Risk Groups: No specific ethnic predispositions have been identified in current literature, suggesting a sporadic occurrence across populations 1 2.

Key Recommendations

Surgical Resection: Aim for gross-total resection when feasible to prevent complications and improve prognosis (Evidence: Strong 1 9).

Comprehensive Imaging: Utilize MRI with contrast for accurate tumor characterization and staging (Evidence: Strong 1 2).

Histopathological Confirmation: Essential for definitive diagnosis, focusing on rosette structures and immunohistochemical markers (Evidence: Strong 1 2).

Regular Follow-Up: Schedule MRI scans every 6-12 months post-resection to monitor for recurrence (Evidence: Moderate 9).

Consider Molecular Profiling: Evaluate for FGFR1 mutations and other genetic alterations to guide management (Evidence: Moderate 5 7).

Postoperative Care: Monitor for and manage complications such as mutism and hydrocephalus (Evidence: Moderate 13).

Radiation Therapy for Inoperable Cases: Consider as a secondary option in cases where surgery is not feasible (Evidence: Weak 4).

Avoid Unnecessary Chemotherapy: Reserve for refractory cases due to low-grade nature of RGNTs (Evidence: Expert opinion 1).

Tailored Management for Special Populations: Adjust surgical and postoperative strategies based on patient age and comorbidities (Evidence: Expert opinion 1 13).

Multidisciplinary Approach: Involve neurosurgeons, radiologists, and oncologists for comprehensive patient care (Evidence: Expert opinion 1 9).

References

1 Altunbüker H, Hinz F, Sahm F, Brehmer S, Wenz H. Incidentally exploring natural course of a rare entity: representative case for rosette-forming glioneuronal tumors. Neurological sciences : official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology 2023. link 2 Zhu D, Cheng A, Benons NTL, Chu S. The rosette-forming glioneuronal tumor mimicked cerebral cysticercosis: a case report. Neurological sciences : official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology 2021. link 3 Chimatira R. Rosette-forming glioneuronal tumor of the cerebellum with intratumoral hemorrhage: case report with radiologic-pathologic correlation in a resource-limited setting. Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery 2026. link 4 Nambirajan A, Sharma MC, Giridhar P, Khanna G, Garg A, Sharma R et al.. Tectal Rosette-Forming Glioneuronal Tumor - A Case Report Focusing on a Possible Role for Radiotherapy in Inoperable Tumors. Neurology India 2021. link 5 Sievers P, Appay R, Schrimpf D, Stichel D, Reuss DE, Wefers AK et al.. Rosette-forming glioneuronal tumors share a distinct DNA methylation profile and mutations in FGFR1, with recurrent co-mutation of PIK3CA and NF1. Acta neuropathologica 2019. link 6 Sekar A, Rudrappa S, Gopal S, Ghosal N, Rai A. Rosette-Forming Glioneuronal Tumor in Opticochiasmatic Region-Novel Entity in New Location. World neurosurgery 2019. link 7 Gessi M, Moneim YA, Hammes J, Goschzik T, Scholz M, Denkhaus D et al.. FGFR1 mutations in Rosette-forming glioneuronal tumors of the fourth ventricle. Journal of neuropathology and experimental neurology 2014. link 8 Thommen F, Hewer E, Schäfer SC, Vassella E, Kappeler A, Vajtai I. Rosette-forming glioneuronal tumor of the cerebellum in statu nascendi: an incidentally detected diminutive example indicates derivation from the internal granule cell layer. Clinical neuropathology 2013. link 9 Zhang J, Babu R, McLendon RE, Friedman AH, Adamson C. A comprehensive analysis of 41 patients with rosette-forming glioneuronal tumors of the fourth ventricle. Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia 2013. link 10 Nandeesh BN, Chabra MS, Babu MK, Chand AK. A rare posterior cranial fossa tumor. Journal of cancer research and therapeutics 2012. link 11 Gessi M, Lambert SR, Lauriola L, Waha A, Collins VP, Pietsch T. Absence of KIAA1549-BRAF fusion in rosette-forming glioneuronal tumors of the fourth ventricle (RGNT). Journal of neuro-oncology 2012. link 12 Ghosal N, Furtado SV, Hegde AS. Rosette forming glioneuronal tumor pineal gland and tectum: an intraoperative diagnosis on smear preparation. Diagnostic cytopathology 2010. link 13 Adachi J, Nishikawa R, Hirose T, Matsutani M. Mixed neuronal-glial tumor of the fourth ventricle and successful treatment of postoperative mutism with bromocriptine: case report. Surgical neurology 2005. link

Rosette-forming glioneuronal neoplasm