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|LETTERS TO EDITOR
|Year : 2018 | Volume
| Issue : 5 | Page : 1512-1514
Are neurocytomas always benign?
R Ramnarayan, D Dutta
Consultant Neurosurgeon, New Hope Hospital, Chennai, Tamil Nadu, India, Consultant Radiation Oncologist, Amritha Medical College, Kochi, Kerala, India
|Date of Web Publication||17-Sep-2018|
Dr. R Ramnarayan
Consultant Neurosurgeon, New Hope Hospital, Chennai, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Ramnarayan R, Dutta D. Are neurocytomas always benign?. Neurol India 2018;66:1512-4
Central neurocytomas are rare supratentorial tumors affecting young adults and are typically located in the lateral ventricles in the region of the foramen of Monro. Such lesions are generally low grade, well circumscribed, and curable by resection alone.
Many case reports of neurocytoma occurring in the extraventricular regions (EVN) have been reported, especially in the thalamus., There have been a few reports of central neurocytomas showing malignant features  and craniospinal dissemination.,, This study presents the report of a young man, who had a thalamic neurocytoma with spinal metastasis.
An 18-year old man presented with features of raised intracranial pressure and gait ataxia. Computed tomography (CT) scan showed a heterogenous minimally enhancing intraventricular lesion. Magnetic resonance imaging (MRI) showed a heterogeneously enhancing infiltrative mass in the right thalamus extending into the third and lateral ventricles and brain stem causing obstructive hydrocephalus [Figure 1], [Figure 2], [Figure 3], [Figure 4]. Multivoxel MR spectroscopy (MRS) revealed elevated choline and lactate and almost total reduction in N-acetyl aspartate (NAA) [Figure 5]. He underwent a right ventriculoperitoneal shunt, and later a stereotactic biopsy. Surprisingly, the stereotactic biopsy confirmed the lesion as a neurocytoma. Histology showed a cellular tumor with sheets of monomorphic round cells with eosinophilic-to-vacuolated cytoplasm and pleomorphic nuclei. On immunohistochemistry, synaptophysin and epithelial membrane antigen (EMA) were positive and cytokeratin and glial fibrillary acidic protein (GFAP) were negative and Ki67 showed an increased vlaue. He underwent postoperative radiotherapy and remained normal for over 2 years.
|Figure 1: Axial T1 weighted image (WI) showing the thalamic lesion extending into the anterior third ventricle and heterogeneously enhancing with contrast|
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|Figure 2: Axial T2WI showing the thalamic lesion extending into the anterior third ventricle|
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|Figure 3: Coronal T1WI showing the right thalamic lesion displacing the third ventricle anterolaterally and minimally, and heterogeneously enhancing on contrast administration|
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|Figure 5: Magnetic resonance spectroscopy (MRS) of the lesion showing a high choline peak (with a reversal of the choline:creatine ratio)|
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He subsequently developed progressive severe back pain and became paraplegic with urinary retention. MRI done showed an intradural extramedullary lesion from D10 to L2 (spinal) levels encasing the nerve roots [Figure 6] and [Figure 7]. The lesion appeared isointense to the cord on T1WI and hyperintense on T2 and STIR imaging and was suggestive of metastasis. MRI brain done at the same sitting showed the right thalamic mass had decreased in size and extent with resolution of the intraventricular component and appeared more necrotic.
|Figure 6: Sagittal view of the spine (T2WI) showing the intradural lesion at the thoracolumbar levels|
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|Figure 7: Sagittal view of spine (T1WI) showing the intradural lesion at the thoracolumabar levels|
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The patient underwent a D10–L1 laminectomy and biopsy with decompression of the lesion. This was also reported as a neurocytoma. The histological findings from the spinal lesion were similar to that of the intracranial one. He was then referred to the medical oncologist and was started on chemotherapy but succumbed during treatment.
Usually central neurocytomas are intraventricular but numerous case reports have now shown that they could be extraventricular also. Brat and colleagues  studied 35 cases of extraventricular neurocytomas; 18 of them were male and 17 female patients. Their age ranged from 5–76 years. All tumors involved the cerebrum. On imaging, these tumors were solitary, variably contrast-enhancing, and often cystic. Nineteen tumors were subtotally resected or biopsied, whereas 14 underwent a gross total excison. Seventeen patients underwent radiotherapy. In 30 cases with an available follow-up, tumor recurrence was seen in 10 cases, with three patients succumbing at 6, 14, and 43 months, respectively. All 10 recurrences followed a subtotal resection. None of the totally resected tumors recurred. Thus, the majority of extraventricular neurocytomas (EVNs) are well differentiated and appear unlikely to recur after gross total resection. Subtotal resection, atypical histologic features, and high cell proliferation rates correlate with recurrence. There have been case reports of extraventricular neurocytomas in the thalamic region with well-documented MRI findings.,,,,,,
Choi et al., noted that though there were some reports of malignant changes in neurocytomas, the majority of the malignant variants rarely recurred after tumor removal and so could be regarded as being benign tumors despite the malignant features seen on histopathology. They then reported a case of malignant variant of the central neurocytoma with a high proliferative index, in which recurrence occurred immediately after surgery and the patient died within 3 months of surgery.
Craniospinal dissemination of neurocytomas has been described by a few studies. Eng et al., reported two cases with a recurrent central neurocytoma that had disseminated through the ventricular system with seeding to the spine, as evidenced by the MRI and a positive CSF cytology. The histological appearance of these two tumors was typical of a neurocystoma and lacked evidence of malignant change. So, the authors cautioned that a central neurocytoma may not be as benign as previously thought, and the recognition of this more malignant behavior has implications for the patient's follow-up and therapy. Ando et al., reported a patient who had imaging studies before surgery that showed a markedly enhancing tumor with small cysts and calcification, which had invaded the adjacent brain parenchyma, and was located in the posterior horn of the right lateral ventricle. Proton magnetic resonance spectroscopy had shown markedly elevated choline and lactate peaks with a strongly diminished N-acetyl aspartate peak. Two years after neurosurgical intervention, the tumor showed craniospinal dissemination in the middle cranial fossa and the intradural extramedullary space of the spine.
Takao et al., described a patient with a tumor that had a high MIB-1 labelling index (4.6%) and dissemination was found to have occurred through the anterior horns of the lateral ventricles and to the spinal cord at the T4 level. The patient underwent partial resection of the tumor with adjuvant radiation treatment for the residual tumor and its disseminated components. After the radiation, the size of the tumor decreased. Stapleton et al., reported a 3-year old boy with a diffuse central neurocytoma with craniospinal dissemination identified at the time of diagnosis. Given the extensive nature of the disease, the patient was placed on chemotherapy. At an 18-month follow-up, the patient has completed six of eight cycles of treatment and the serial imaging had revealed a stable disease within the craniospinal axis.
In our case, this patient presented with a thalamic lesion that had turned out to be a neurocytoma. He presented later with spinal metastasis. We, therefore, suggest that when neurocytomas are extraventricular and have aggressive histology, repeated clinical assessments and spinal screening also may be indicated. However, larger series of cases are needed to frame a proper policy.
The elder brother of the patient has consented to the submission of this report to the journal. The authors also declare that there is no conflict of interest in this study and there is no financial support obtained.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]