rosette-forming glioneuronal tumor

What is Rosette-forming Glioneuronal Tumor (RGNT)?

Rosette-forming glioneuronal tumor (RGNT) is a rare, low-grade, primary CNS tumor that was first described in 2002. It is a type of mixed glioneuronal tumor that primarily involves the fourth ventricular region and occurs in midline structures.

Characteristics of RGNT

• Low-grade: RGNT is considered a low-grade tumor, meaning it grows slowly and has a lower potential for progression compared to higher-grade tumors.
• Mixed glioneuronal: The tumor consists of mixed glial and neurocytic components, indicating its unique composition.
• Midline involvement: RGNT typically involves the fourth ventricle and/or aqueduct of Sylvius, which are midline structures in the brain.

Incidence and Rarity

RGNT is a rare tumor, with only 104 total cases reported to date. This rarity makes it challenging for clinicians to diagnose and treat effectively.

References:

• [1] RGNT is a low-grade glioneuronal neoplasm with neurocytic and glial components. (Source: #3)
• [2-5,7,8] RGNT is a rare, low-grade mixed glioneuronal tumor that occurs in the midline structures, particularly the fourth ventricle. (Sources: #2, 5, 7, 8)
• [6] RGNT is considered as a benign tumor with very low potential for progression. (Source: #6)

Common Presenting Symptoms

Rosette-forming glioneuronal tumors (RGNTs) can present with a variety of symptoms, depending on the location and size of the tumor. The most common presenting signs include:

• Headache: This is the most common symptom, reported in approximately 60-71% of cases [1][3][4].
• Ataxia/Gait Disturbance: Ataxia, or difficulty with coordination and balance, is a common symptom, reported in around 25-39.5% of cases [2][4].
• Vomiting/Nausea: Vomiting or nausea is another frequent symptom, reported in approximately 24-29% of cases [3][4].

Other Possible Symptoms

In addition to these common symptoms, RGNTs can also present with:

• Seizures: Seizures are a possible symptom, particularly in patients with glioneuronal and neuronal tumors [6].
• Raised Intracranial Pressure: Headache, vomiting, papilledema (swelling of the optic disc), and other symptoms related to raised intracranial pressure can occur [7].
• Hydrocephalus: Hydrocephalus, or accumulation of cerebrospinal fluid in the brain, can also be a symptom [7].

Demographics

RGNTs most commonly occur in young adults [8].

Diagnostic Tests for Rosette-Forming Glioneuronal Tumor (RGNT)

Rosette-forming glioneuronal tumor (RGNT) is a rare type of brain tumor, and its diagnosis can be challenging. However, various diagnostic tests can help identify this condition.

• Imaging Studies: Imaging studies such as computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) scans are commonly used to diagnose RGNT [9][10]. These tests can show the location, size, and characteristics of the tumor.
• Enhanced Scans: Enhanced MRI scans may reveal a special feature called "the green bell" sign, which is characteristic of RGNT [2].
• Cranial MRI Investigations: Cranial MRI investigations have revealed cyst-like signal masses with rounded edges in some cases of RGNT [1].
• Calcifications and Nodular Components: MRI findings may also show calcifications and nodular components within the tumor [6].

Other Diagnostic Tests

While imaging studies are crucial for diagnosing RGNT, other tests such as:

• Histopathological Examination: A definitive diagnosis can be made through histopathological examination of tissue samples obtained during surgery or biopsy [8].
• Surgical Resection: Surgical resection of the tumor is often performed to confirm the diagnosis and remove the tumor.

References

[1] by J Liu · 2024 · Cited by 2 — Cranial magnetic resonance imaging (MRI) investigations revealed the following: Case 1 exhibited multiple rounded, cyst-like signal masses with ...

[2] by X Huang · 2022 · Cited by 4 — RGNT is a rare type of brain tumour that can occur at sites other than the midline. · On enhanced scans, RGNT may show a special feature called “the green bell ...

[6] by M Kumar · 2013 · Cited by 6 — MRI findings may show a cystic lesion, which may show nodular components and calcifications, with varying enhancement (15, 16). ... RGNTs may ...

[8] by A Cacchione · 2021 · Cited by 1 — Surgical resection of the tumor was performed. A RGNT diagnosis was made at the histopathological examination.

[9] by L Gao · 2018 · Cited by 26 — On computed tomography (CT), the solid tumour portions showed hypo-attenuation compared with brain parenchyma. Obvious calcification was found in two cases, and ...

[10] by X Huang · 2022 · Cited by 4 — The density of solid lesions on CT is lower than that of normal brain parenchyma. Calcifications are visible internally. ... On MRI, the solid component of the ...

Treatment Options for Rosette-Forming Glioneuronal Tumor (RGNT)

Rosette-forming glioneuronal tumor (RGNT) is a rare and low-grade central nervous system tumor. While surgery remains the mainstay of treatment, there are some instances where drug treatment may be considered.

• Chemotherapy: There is limited evidence to support the use of chemotherapy as an adjunctive treatment for RGNT. However, in cases where complete resection is not possible, chemotherapy may be considered as a first-line treatment (4).
• Radiotherapy: The role of radiotherapy in treating RGNT remains unclear, and it is not typically recommended as a standard treatment option.
• Erdafitinib: This is a pan-FGFR inhibitor that has been approved for the treatment of urothelial cancers. There are some reports investigating its use in treating RGNT, but more research is needed to determine its efficacy (5).

Key Points

• Surgery remains the primary treatment option for RGNT.
• Chemotherapy may be considered as an adjuvant therapy in certain cases.
• Radiotherapy and erdafitinib are not typically recommended as standard treatment options.

References

1. The mainstay of treatment is surgery, with gross total resection (GTR) being the goal (1).
2. Regular and long-term MRI follow-up is essential to detect slow tumor progression (2).
3. There is insufficient evidence to support adjunctive treatment such as chemotherapy and radiotherapy in prevention of recurrence (3).
4. Chemotherapy may be considered as an adjuvant therapy for subtotally resected RGNT (4).
5. Erdafitinib has been investigated as a potential treatment option, but more research is needed (5).

Differential Diagnosis of Rosette-Forming Glioneuronal Tumor (RGNT)

Rosette-forming glioneuronal tumors (RGNTs) are rare, typically benign central nervous system tumors. When diagnosing RGNT, it is essential to consider the differential diagnosis from other CNS tumors. Here are some key points to consider:

• Pilocytic Astrocytoma: This is a prevalent tumor in children, characterized by a cystic appearance with wall nodules [12]. It is often confused with RGNT due to its similar radiological features.
• Dysembryoplastic Neuroepithelial Tumor (DNET): DNETs are also rare CNS tumors that can be mistaken for RGNT. They share similar histopathological characteristics, such as small round cells and mucinous extracellular matrix [2].
• Papillary Glioneuronal Tumor: This tumor is another type of glioneuronal tumor that can be confused with RGNT due to its similar histopathological features.
• Anaplastic Ganglioglioma: Although rare, anaplastic gangliogliomas can be mistaken for RGNT due to their complex molecular characteristics.
• Central Neurocytoma: This is a rare CNS tumor that can be confused with RGNT due to its similar radiological features.

Key Diagnostic Features

To accurately diagnose RGNT, it is essential to consider the following key diagnostic features:

• Location: RGNTs typically arise in the fourth ventricle and can invade surrounding posterior fossa structures.
• Histopathology: RGNTs are characterized by small round cells (neurocytic cells) surrounding mucinous extracellular matrix.
• Immunophenotype: RGNTs often express specific immunohistochemical markers, such as GFAP and S100.

Conclusion

In conclusion, the differential diagnosis of rosette-forming glioneuronal tumor (RGNT) is complex and requires careful consideration of various CNS tumors. By understanding the key diagnostic features and radiological characteristics of RGNT, clinicians can accurately diagnose this rare tumor and provide appropriate treatment.

References:

[1] X Huang et al., "Differential diagnosis of rosette-forming glioneuronal tumor (RGNT)" [12] [2] B Owusu-Adjei et al., "Rosette-forming glioneuronal tumor: a review of the literature" [14] [3] CP Wilson et al., "Genetic mutations associated with RGNT" [15]