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LETTER TO EDITOR
Year : 2017  |  Volume : 65  |  Issue : 1  |  Page : 202-205

Extraventricular neurocytoma: An uncommon tumor in a young boy. A review of literature


1 Department of Histopathology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
2 Department of Neurosurgery, Postgraduate Institute of Medical Education and Research, Chandigarh, India

Date of Web Publication12-Jan-2017

Correspondence Address:
Kirti Gupta
Department of Histopathology, Postgraduate Institute of Medical Education and Research, Chandigarh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.198201

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How to cite this article:
Agrawal P, Gupta K, Sodhi HB. Extraventricular neurocytoma: An uncommon tumor in a young boy. A review of literature. Neurol India 2017;65:202-5

How to cite this URL:
Agrawal P, Gupta K, Sodhi HB. Extraventricular neurocytoma: An uncommon tumor in a young boy. A review of literature. Neurol India [serial online] 2017 [cited 2017 Feb 23];65:202-5. Available from: http://www.neurologyindia.com/text.asp?2017/65/1/202/198201


Sir,

Extraventricular neurocytomas (EVNs) are rare parenchymal tumors with features of a neurocytoma located in the cerebral hemispheres.[1],[2] While these have been often reported in adults, examples of such tumors in the pediatric population are extremely uncommon.[3],[4] Morphologically, these are characterized by features almost similar to that seen in central neurocytomas, except for the presence of a conspicuous glial or ganglionic differentiation. In addition, they often demonstrate features suggestive of a higher grade, which are important to recognize in view of their aggressive behavior. We describe an example of such tumor arising in the frontal lobe in a 10-year-old boy and discuss its differential diagnosis and molecular abnormalities.

A 10-year-old boy presented with complaints of a single episode of simple partial seizure involving the right upper and lower limb. This was associated with mild non-localizing headache; however, there were no signs of raised intracranial pressure. On examination, there were neither sensory-motor deficits nor evidence of papilledema on fundus examination. Noncontrast computerized tomography (CT) of the head demonstrated a hyperdense lesion in the left inferior frontal region with areas of calcification and bleed. Gadolinium enhanced magnetic resonance imaging (MRI) showed a T1-weighted (TW1)/T2-weighted (TW2) heterogenous lesion with an irregular rim (hyperintense on T1W and hypointense on T2W images, suggestive of bleed). The lesion was heterogenously contrast enhancing and located in the left inferior frontal gyrus, extending to the left frontal horn [Figure 1]a, [Figure 1]b, [Figure 1]c, [Figure 1]d, [Figure 1]e. With the radiological impression of a primitive neuroectodermal tumor, the patient underwent a left frontal craniotomy and gross total resection of the lesion. Intraoperatively, the lesion was grayish, soft, and vascular with areas of necrosis and bleed. There was a small part of the tumor going into the left frontal horn, which was also removed. The postoperative clinical recovery was good and the patient did not have any neurological deficits, although he had one episode of focal seizure on the first postoperative day.
Figure 1: (a) Noncontrast axial computed tomography image showing a heterogenous hyperdense lesion with areas of bleed and calcification; (b) T1-weighted (T1W) axial magnetic resonance imaging (MRI) image showing a heterogenous lesion with a hyperintense rim, with an intraventricular extension; (c) T2-weighted axial MRI image showing a heterogenous lesion with a hypointense rim, with intraventricular extension; (d) T1W axial gadolinium image showing the heterogenous contrast enhancement; (e) T1W sagittal gadolinium image showing the intraventricular extension

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Morphologically, the resected tumor fragments demonstrated a sharp interface with the non-neoplastic brain, indicating the presence of a noninfiltrative lesion. Monomorphic round cells with stippled chromatin were dispersed in a fine neuropil stroma, interspersed by fine capillary channels and laminated concentric microcalcifications [Figure 2]a, [Figure 2]b, [Figure 2]c. No significant pleomorphism was noted within the tumor cells. Rosettes-like structures with central fibrillar neuropil cores were also present. In a few fragments, occasional mitotic figures (3/10 hpf), areas of necrosis, and endovascular proliferation were also detected [Figure 2]d. No ganglion cell differentiation was noted. The tumor cells were strongly immunoreactive for synatophysin [Figure 3]a, and negative for glial fibrillary acidic protein (GFAP), epithelial membrane antigen (EMA) and isocitrate dehydrogenase (IDH) 1/2 immunostain. Focal glial differentiation was highlighted with the glial fibrillary acid protein (GFAP) immunostain [Figure 3]b. The tumor was negative for 1p/19q codeletion, when assessed by the fluorescent in-situ hybridization. The tumor was categorized as an extraventricular central neurocytoma, World Health Organization (WHO) grade II, with atypical features.
Figure 2: (a): Low magnification of the tumor characterized by sheets of monomorphic round cells interspersed by microcalcification (hematoxylin and eosin [H and E] ×200); (b) tumor cells are arranged in a background of finely fibrillar neuropil cores (H and E ×400); (c) monomorphic round cells with finely stippled chromatin with mitotic figure also being noted [arrow] (H and E ×1000); (d) Foci of endovascular proliferation (H and E ×400)

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Figure 3: (a) Robust, diffuse immunoreactivity for synaptophysin (immunoperoxidase ×200); (b) focus of glial differentiation highlighted by glial fibrillary acidic protein (immunoperoxidase ×400)

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Well-differentiated neuronal neoplasms composed of neurocytes arising within the ventricular system near the foramen of Monro are designated as central neurocytoma. Morphologically, similar tumors arising in the cerebral hemispheres or spinal cord parenchyma are referred as EVN.[1] This was recognized as a distinct entity in the 2007 WHO classification of central nervous system tumors.[2] These tumors are most commonly located in the frontal and parietal lobes.[1],[3],[4] Examples of such tumors have also been described in the infratentorial region,[5],[6] thalamus,[6] and spinal cord.[7],[8] EVNs mostly occur in adults, while pediatric examples have been reported exclusively as isolated case reports in the literature [Table 1].[3], 4, [8],[9],[10],[11],[12],[13],[14],[15],[16],[17],[18],[19],[20],[21],[22],[23] With the prevalence of EVN in the frontal lobe, seizure activity is the most common presenting symptom, as also noted in this child, followed by headache and cranial nerve palsy. Recently, behavioral disorders as presenting symptoms have also been described.[3] As the majority of tumor mass is confined to the extraventricular location, i.e., in the frontal lobe, it is categorized as an EVN in the present case. Morphologically, EVNs differ from central neurocytoma in exhibiting a conspicuous ganglionic and focal glial differentiation.[17] Moreover, EVNs are more likely to show high grade features with a tendency towards an aggressive behavior,[1],[22],[24] which underscores the importance of diagnosing this tumor correctly and achieving a gross total resection.
Table 1: Clinical and morphological characteristics of pediatric extraventricular neurocytoma reported in the literature

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Microscopically, these have to be differentiated from oligodendroglioma (ODG) with neurocytic differentiation,[25] oligoastrocytoma (OA) with neurocytic differentiation, ganglioglioma (GG), dysembryoplastic neuroepithelial tumor (DNET), and papillary glioneuronal tumors (PGNT). Both ODGs and OAs are infiltrative tumors, with ODGs characterized by 1p/19q codeletion in a majority of cases. GGs are characterized by a conspicuous population of ganglion and glial cells forming the bulk of tumor unlike an EVN. DNETs have a nodular appearance which overruns the cortex. Histologically, they have a low cellularity, comprising oligodendroglia-like cells and floating neurons. PGN tumors are histologically distinguishable by their papillary or pseudopapillary architecture with perivascular small astrocytes and interpapillary neurocytes.

Due to its rarity, there is little information in the literature regarding the molecular abnormalities of EVNs. Recently, Rodriquez et al., have explored the prevalence of 1p/19q codeletion and t(1;19) in EVN. Their results indicate that a subset of EVNs harbors 1p/19q loss and t(1;19), which is associated with an aggressive histology.[26] It is interesting to note that, as compared to ODG, a similar chromosomal codeletion in EVN does not offer any survival benefits; rather, it indicates a more aggressive phenotype.[13],[27] Furthermore, in a series of seven patients of EVNs, Myung et al., observed absence of IDH1/2 mutations, α-internexin, and p53 in all the seven cases.[4] A single case with polysomy of epidermal growth factor receptor gene was identified but none of the cases in their series harbored a 1p/19q codeletion.

In a recent study comparing the features in intraventricular central neurocytomas and EVNs, it was observed that EVNs more frequently displayed malignant biologic behavior associated with atypia, higher recurrence rate, and shorter time to recurrence. Total surgical resection is the treatment of choice offering a substantially good outcome.[21],[28] Although the literature on EVN is limited, larger series with a longer follow-up data are required to guide the management protocols.

In conclusion, intraparenchymal tumors composed of neurocytic cells with focal glial or ganglionic differentiation, rarely may also arise in the cerebral hemispheres in children, and should be considered in the list of differential diagnosis. As these are often associated with an aggressive clinical behavior, presence of high grade features should be carefully searched for. Recognizing their histological features is crucial in avoiding the misdiagnosis of these tumors as primitive neuroectodermal tumors or high grade glial tumors.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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