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|LETTERS TO EDITOR
|Year : 2016 | Volume
| Issue : 1 | Page : 180-182
Atypical thalamic neurocytoma: A rare neoplasm
Kanwaljeet Garg1, Chinmaya Dash1, Aanchal Kakkar2, Meher Chand Sharma2, Pankaj Kumar Singh1, Bhawani Shankar Sharma1
1 Department of Neurosurgery, All Institute of Medical Sciences, New Delhi, India
2 Department of Pathology, All Institute of Medical Sciences, New Delhi, India
|Date of Web Publication||11-Jan-2016|
Pankaj Kumar Singh
Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Garg K, Dash C, Kakkar A, Sharma MC, Singh PK, Sharma BS. Atypical thalamic neurocytoma: A rare neoplasm. Neurol India 2016;64:180-2
Neurocytomas are rare tumors of the central nervous system, usually considered benign, and are typically located in the supratentorial ventricular system near the foramen of Monro. A more aggressive variant of this tumor called an atypical neurocytoma was reported in 1989. We describe a thalamic atypical neurocytoma. Ours is the second case of thalamic atypical neurocytoma reported in the English literature.
A 16-year-old female patient presented with a 6-month history of progressively increasing headache, vomiting, and visual blurring. Physical examination revealed decreased visual acuity, 6/18 on the right side and 6/9 on the left side, with bilateral papilledema on fundus evaluation. She also had left-sided hemiparesis (Medical Research Council grade 4/5), associated with exaggerated deep tendon reflexes on the left side.
Magnetic resonance imaging (MRI) revealed a juxtaventricular 4 × 3.5-cm mass lesion in the right posterior thalamic region, hyperintense on T1- and T2-weighted imaging, with ventriculomegaly. On contrast administration, the lesion showed a heterogenous contrast enhancement [Figure 1].
|Figure 1: Contrast-enhanced MRI coronal (a), axial (b), and sagittal sections (c) showing a heterogeneously enhancing lesion in the right posterior thalamic region with hydrocephalous|
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The patient underwent a right occipital craniotomy and near-total excision of the tumor by the transcortical transventricular approach. Patient did well after surgery. There were no new deficits in the postoperative period, and the power on the left side also recovered to normal. [Figure 2] shows the histopathological examination of the surgical specimen with description of histopathological findings. MIB-1 labeling index (LI) calculated in the highest proliferating areas was 13%. Postoperative MRI revealed a small residual tumor in the posterior third ventricular region. Radiotherapy was given, and postradiotherapy MRI [Figure 3] showed no evidence of recurrence. The patient was doing well at a follow up of 40 months.
|Figure 2: (a) Photomicrographs show a tumor composed of monomorphic round cells with interspersed fibrillary areas and thin vascular channels. (b) The tumor cells have uniform round nuclei with speckled chromatin and show increased mitotic activity. (c) On immunohistochemistry, the tumor cells show positivity for synaptophysin, and (d) nuclear NeuN positivity. (e) GFAP highlights entrapped reactive astrocytes, while tumor cells are negative. (f) MIB-1 LI is elevated|
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|Figure 3: Postoperative contrast-enhanced brain MRI axial sequence showing postoperative changes with no recurrenceT2-weighted|
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Central neurocytomas are uncommon tumors, with their incidence ranging from 0.1% to 0.5% of all intracranial tumors. The term “atypical” or proliferating neurocytoma has been proposed for tumors if they exhibit an MIB-1 labelling index (LI) >2% or atypical histologic features, such as nuclear pleomorphism, necrosis, microvascular proliferation, and brisk mitotic activity (>3/10 high-power fields). For an extraventricular neurocytoma (EVN), frontal and parietal lobes represent the predominant location, followed by other rare sites, including the cerebellum, brainstem, thalamus, amygdala, pineal gland, retina, and spinal cord. These EVN can pose a diagnostic difficulty and can be confused with an oligodendroglioma.
Atypical neurocytomas behave more aggressively than the typical central neurocytomas. Complete resection offers better local control and survival as compared with incomplete resection and radiotherapy. A total surgical resection, if feasible, may be potentially curative.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]