Tumor control of third ventricular central neurocytoma after gamma knife radiosurgery in an elderly patient: A case report and literature review

Epigenetic Alteration of H3K27me3 as a Possible Oncogenic Mechanism of Central Neurocytoma

Central neurocytoma (CN) is a low-grade neuronal tumor that mainly arises from the lateral ventricle (LV). This tumor remains poorly understood in the sense that no driver gene aberrations have been identified thus far. We investigated immunomarkers in fetal and adult brains and 45 supratentorial periventricular tumors to characterize the biomarkers, cell of origin, and tumorigenesis of CN. All CNs occurred in the LV. A minority involved the third ventricle, but none involved the fourth ventricle. As expected, next-generation sequencing performed using a brain-tumor-targeted gene panel in 7 CNs and whole exome sequencing in 5 CNs showed no driver mutations. Immunohistochemically, CNs were robustly positive for FGFR3 (100%), SSTR2 (92%), TTF-1 (Nkx2.1) (88%), GLUT-1 (84%), and L1CAM (76%), in addition to the well-known markers of CN, synaptophysin (100%) and NeuN (96%). TTF-1 was also positive in subependymal giant cell astrocytomas (100%, 5/5) and the pituicyte tumor family, including pituicytoma and spindle cell oncocytoma (100%, 5/5). Interestingly, 1 case of LV subependymoma (20%, 1/5) was positive for TTF-1, but all LV ependymomas were negative (0/5 positive). Because TTF-1-positive cells were detected in the medial ganglionic eminence around the foramen of Monro of the fetal brain and in the subventricular zone of the LV of the adult brain, CN may arise from subventricular TTF-1-positive cells undergoing neuronal differentiation. H3K27me3 loss was observed in all CNs and one case (20%) of LV subependymoma, suggesting that chromatin remodeling complexes or epigenetic alterations may be involved in the tumorigenesis of all CNs and some ST-subependymomas. Further studies are required to determine the exact tumorigenic mechanism of CN.

Endoscopic approach and stereotactic radiosurgery for a posterior third ventricular Central Neurocytoma - case report and literature review

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Central Neurocytomas are a rare intracranial tumour, often presenting with obstructive hydrocephalus.

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Isolated lesions in the posterior third ventricle are an uncommon location for Central Neurocytomas.

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An endoscopic approach to these allows for concurrent biopsy and therapeutic cerebrospinal fluid diversion.

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Adjuvant Stereotactic Radiosurgery improves outcomes of survival and local control in subtotal resection.

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Together, this is a viable treatment for deep-seated, posterior third ventricular Central Neurocytomas.

Introduction

Central Neurocytomas (CN) are a rare intracranial tumour, most often arising in the lateral ventricles and presenting with obstructive hydrocephalus. Isolated lesions in the third ventricle are uncommon. We present the fourth reported case of posterior third ventricular CN successfully managed surgically via endoscopy, allowing for concurrent biopsy and therapeutic endoscopic third ventriculostomy (ETV). Stereotactic radiosurgery was administered for the residual lesion. A brief review of CNs and previous similar cases is also provided.

Presentation of case

A 58-year-old male presented with progressive decline in cognition and gait. Subsequent Magnetic Resonance Imaging revealed obstructive hydrocephalus secondary to a posterior third ventricular lesion. An endoscopic biopsy and concurrent cerebrospinal fluid diversion by ETV was performed. Pathological analysis was consistent with a CN with positivity to Synaptophysin. MIB-1 proliferation index was 1%. There was good clinical recovery, and the patient underwent adjuvant stereotactic radiosurgery 1.5 months post-surgery.

Discussion

Due to the rarity of CNs arising from the third ventricle, there are only three previous reports of these approached endoscopically. Such a technique allows for good visualisation of the lesion, and therapeutic ETV to relieve obstructive hydrocephalus. This case supports this approach as a valid, minimally invasive option. Additionally, this is the first case to report the MIB-1 proliferation index, contributing to future outcome evaluation of endoscopic approaches to typical (MIB-1 < = 2%) verses atypical (MIB-1 > 2%) CNs.

Conclusion

Endoscopic biopsy with concurrent ETV and adjuvant stereotactic radiosurgery is a valid treatment option for deep seated isolated small posterior third ventricular CNs.