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|LETTER TO EDITOR
|Year : 2016 | Volume
| Issue : 2 | Page : 340-343
Angiocentric glioma of hippocampus–report of a rare intractable epilepsy-related tumor
Debajyoti Chatterjee1, Kirti Gupta1, Navneet Singla2, Bishan Dass Radotra1
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 Publication||3-Mar-2016|
Additional Professor, Department of Histopathology, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Chatterjee D, Gupta K, Singla N, Radotra BD. Angiocentric glioma of hippocampus–report of a rare intractable epilepsy-related tumor. Neurol India 2016;64:340-3
Angiocentric glioma is a rare astrocytic tumor of the central nervous system (CNS) recognized as a distinct entity almost a decade ago.,, It is a slow-growing tumor, commonly associated with epilepsy in children and young adults. Histologically, this tumor is characterized by an angiocentric growth composed of spindle-shaped cells with features of ependymal differentiation. We describe the imaging and histological features in a case of angiocentric glioma (AG) arising within hippocampus in a young lady presenting with typical history of intractable seizures.
A 22-year-old lady presented with a long history of intractable seizures, which were resistant to medical management. On magnetic resonance imaging (MRI), she was found to be having a hyperintense right mesial temporal lobe lesion on T2-weighted imaging. This was mildly hypointense to heterogeneous in intensity on T1-weighted imaging with no contrast enhancement. Flair sequences of MRI showed altered signal changes in the same area [Figure 1]a,[Figure 1]b,[Figure 1]c,[Figure 1]d. With video electroencephalogram, clinico-physiological and radiological concordance of epileptogenic focus was ascertained to the right mesial temporal lobe. Right amygdalo-hippocampectomy was performed and the excised mass was submitted for histopathological examination. Histologically, a low-grade glial tumor with low cellularity was identified along with fragments of normal cortex. The tumor was characterized by a prominent perivascular arrangement with cells oriented in a linear fashion around the vessels [Figure 2]a and [Figure 2]b. No rosette formation was identified. The individual cells were spindle shaped with minimal pleomorphism, oval nuclei with vesicular chromatin. A small focus also revealed compact areas arranged in streaming “schwannoma-like” fascicular pattern [Figure 2]c. No features of anaplasia in the form of mitoses, necrosis, or endothelial proliferation was identified. No subpial spread was detected. The tumor cells demonstrated immunoreactivity for glial fibrillary acidic protein (GFAP) and distinctive dot-like positivity for epithelial membrane antigen (EMA) [Figure 2]d and [Figure 2]e. Thus, the tumor was categorized as AG (WHO Grade I). The patient was seizure-free at 6 months of follow-up.
|Figure 1: (a) T2-weighted magnetic resonance imaging showing hyperintense lesion in the right mesial temporal lobe. (b) T1-weighted magnetic resonance imaging showing a mildly hypointense to heterogeneous intensity lesion in the right mesial temporal lobe. (c) Flair sequences of magnetic resonance imaging showing altered signal changes in the same area. (d) Contrast magnetic resonance imaging showing no contrast enhancement|
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|Figure 2: (a and b) Tumor exhibits a prominent and distinctive angiocentric pattern. Spindle-shaped cells with perpendicular orientation around the vessels (H and E, ×200). (c) Focal areas with a nodular and fascicular arrangement of tumor cells (H and E, ×100). (d) Immunoreactivity for glial fibrillary acidic protein within the tumor cells (immunoperoxidase, ×200). (e) Characteristic dot-like immunoreactivity for epithelial membrane antigen within the tumor cells (immunoperoxidase, ×200)|
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AG was categorized as a distinct entity in 2007 WHO classification of CNS tumors and regarded as a Grade I tumor. Around 70 cases have been reported in literature so far. It is a relatively uncommon tumor arising in children and young adults (range 2–70 years, mean age 16 years)., They commonly present with long-standing intractable epileptic seizures.,, Besides AG, other lesions associated with refractory seizures include mesial temporal sclerosis, focal cortical dysplasia (FCD), vascular malformation, nodular heterotopia and tumors. Among the neoplasms, ganglioglioma (GG) is the commonest tumor associated with epilepsy; others include low-grade glioma/glioneuronal tumor, dysembryoplastic neuroepithelial tumor, AG and meningioangiomatosis.,,
AGs are superficial tumors occurring in the frontal lobe, followed in frequency by the temporal and parietal lobe. They may extend to the underlying white matter and a “stalk-like” extension to the ventricle has been described as pathognomonic. The radiological features of AG are quite characteristics, though not diagnostic, with T2-weighted and fluid attenuated inversion recovery-hyperintensity that lacks enhancement following contrast administration. Cystic changes may be present in a minority of cases. Histologically, the defining features include monomorphous tumor cells arranged around the vessels in an angiocentric pattern., The cells are slender, spindle-shaped, and often are oriented perpendicular to the vessels. Although not present in the index case, the perpendicularly oriented subpial spread of tumor cells is identified in a subset of this tumors and is a useful morphological feature that helps in the diagnosis. Some examples may display a solid growth pattern with clusters of cells arranged on nodular “schwannoma-like” pattern, as identified in the present case. Epithelioid and round cell morphology has also been described in a few examples with these two being described as variant cases within the spectrum of AG., Atypical features including mitoses and anaplasia are sometimes encountered, though the criteria for anaplasia are not well established in the WHO classification. The accompanying cortex may show features of focal cortical dysplasia; these were, however, not detected in the present case. Immunoreactivity for glial fibrillary acidic protein (GFAP), S-100 and vimentin is strong and consistent. Immunoreactivity for epithelial membrane antigen (EMA) is similar to that seen with an ependymoma, i.e., having surface and paranuclear dot-like appearance.,, Ultrastructurally, they show features of ependymal differentiation. Their cell of origin is controversial; however, they are best regarded as astrocytic tumors with an ependymal differentiation., Studies exploring the molecular abnormalities within this tumor by chromosomal comparative genomic hybridization have revealed loss of chromosomal bands at 6q24 to q25. Interestingly, focal deletion of the terminal region of MYB on chromosome 6q23 was seen in 1 of 2 AG evaluated within a large cohort of low-grade gliomas. Also, increased expression of MYB was demonstrated by quantitative reverse transcriptase- polymerase chain reaction and immunohistochemistry. Amplification of MYB, an oncogene not previously implicated in gliomagenesis, was also detected in two diffuse astrocytomas in the same cohort. While the molecular abnormalities could not be explored in the present case, the peculiar morphological features of bipolar spindle cells, angiocentric pattern of arrangement, their subpial spread, and the low-grade nature are very helpful clues for their correct diagnosis. Gangliogliomas (GG), pilocytic astrocytomas (PA), and subependymomas are the other entities in the differential diagnosis of AG. The normal yet entrapped ganglion cells in AG should be carefully differentiated from dysmorphic ganglion cells of GG. PAs are contrast-enhancing tumors with dense fibrillary architecture and rarely demonstrate an angiocentric pattern. Subependymomas are noninfiltrative with a nodular architecture, small round cells, clustered together, with pale acellular zones in between.
The seizure outcome following surgical excision of the tumor is excellent, and most of the patients with AG experience long-term seizure-free survival. AG is a slow-growing tumor and shows a low proliferative index. Gross total excision is curative and recurrence is extremely rare. It is important to distinguish an AG from a Grade II astrocytoma, as these patients do not need any additional therapy in the form of radiotherapy or chemotherapy and experience an excellent outcome.
We describe a case of a young adult with AG arising in the mesial temporal lobe manifesting with refractory seizures. The histological features were characteristic with immunopositivity for GFAP and dot-like positivity with EMA clinching the diagnosis. It is pertinent to recognize its histology to prevent overinterpreting this tumor as an infiltrating Grade II glioma. Despite their infiltrating nature, these are slow-growing and gross resection of the tumor is curative.
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[Figure 1], [Figure 2]