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CASE REPORT |
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| Year : 2008 | Volume
: 3
| Issue : 2 | Page : 160-162 |
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Astroblastoma: A radio-histological diagnosis
Nilesh S Kurwale, Deepak Agrawal, Bhawani Shankar Sharma
Department of Neurosugery and Gamma Knife, All India Institute of Medical Sciences, New Delhi - 110 029, India
Correspondence Address:
Nilesh S Kurwale
7/53, Gents Hostel, AIIMS, Ansari Nagar, New Delhi
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/1817-1745.43649
 Abstract | | |
Astroblastoma is thought to arise from astroblast - an intermittent cell between spongioblast and astrocytes and is a rare tumor in the pediatric age group. The histological appearance are characterized by radiating arrangement of spindle-shaped tumor cells forming perivascular pseudorosettes, and being very similar to that seen in ependymomas, makes differentiation difficult. The authors report the case of a 5-year-old girl who had a large frontal tumor, which was thought to be an astroblastoma preoperatively, based on the unique magnetic resonance imaging features these tumors have. The histological findings, in association with the preoperative radiology confirmed the diagnosis of astroblastoma. The authors conclude that the MR imaging of astroblastomas is extremely helpful in differentiating from ependymomas and is used for preparing the histopathology reports in these patients.
Keywords: Astroblastoma, glial brain tumors, pediatric brain tumor
How to cite this article:
Kurwale NS, Agrawal D, Sharma BS. Astroblastoma: A radio-histological diagnosis. J Pediatr Neurosci 2008;3:160-2 |
| Introduction | |  |
Today's neurosurgeons realize that histopathology in isolation may not be able to provide a clear diagnosis in significant number of their patients with tumors, and they will have to depend on the advances in immunohistochemistry, molecular biology, and neuro-imaging to provide a 'working' diagnosis. This is especially noticeable in rare tumors such as astroblastomas, which are histologically similar to ependymomas and are usually confused for the latter. However, if the histology is correlated with the patient's radiology, then the differentiation can easily be made. We report a case of astroblastoma and describe some unique imaging characteristics of these rare tumors which may make the diagnosis apparent preoperatively.
| Case Report | | |
A 5-year-old girl presented with intermittent frontal headache and episoic vomiting of 8 months duration. There were also two episodes of generalized tonic clonic in this period. On examination, except for bilateral papilloedema no other clinical abnormality was detected. Routine blood investigations were within normal limits. A contrast magnetic resonance imaging (MRI) of the brain showed a large well-defined solid-cystic mass in the right frontal region extending from the cortex to the periventricular region with intense contrast enhancement [Figure 1] and lack of peritumoral edema. The solid portion had a heterogenous appearance and was isointense to grey matter on T2 weighted images. In view of these characteristic imaging findings, a preoperative diagnosis of astroblastoma was entertained. The patient underwent a right frontal craniotomy with gross total excision of tumor. Intraoperatively, there was a large solid-cystic, moderately vascular, Cavitron ultrasonic surgical aspirator (CUSA) suckable tumor in the right frontal region without any evidence of necrosis or vein thrombosis. Sections examined showed a tumor comprising of round to oval cells in a fibrillary background forming perivascular pseudorosettes with thick short processes radiating toward the blood vessels [Figure 2A],[Figure 2B]. There was no evidence of necrosis, mitosis, or endothelial hyperplasia. The tumor cells were immunopositivity for glial fibrillary acidic protein (GFAP), which was more marked in the perivascular cell processes [Figure 2C],[Figure 2D]. The postoperative period was uneventful and the patient was referred for chemo-radiotherapy and continued to be on follow-up.
| Discussion | | |
Astroblastoma, a rare tumor of cerebral hemispheres and has been known to occur from infancy to fifth decade. [1],[2],[3],[4] The cell of origin of astroblastoma is still a debatable entity, but widely accepted to be the astroblast - an intermittent cell between spongioblast and astrocytes. Till recently, the possible origin form tanycyte was reported, [5],[6] however; till date no consensus has been reached whether it arises from an immature astroblast or by process of differentiation of astrocytes. [5] Clinically raised intracranial pressure and seizure episodes remain the common presentation. Other may present with signs and symptoms pertaining to anatomical structures involved like visual loss, memory disturbances seizures, weakness, and altered sensorium. [2],[3],[7] Cerebral hemispheres, mostly frontal and occipital lobes are the site favored by these tumors as in our case also but corpus callosum, cerebellar hemispheres, optic nerves and brainstem, and also cauda equina tumors have been reported in the literature. [5],[8]
On MRI, these tumors tend to be large lobulated masses which characteristically extend from the peripheral cortex to the periventricular region. On imaging, these tumors are well-demarcated lobular tumors. T1 and T2 weighed sequences of these tumors appear well demarcated, heterogeneous solid-cystic components with inhomogeneous contrast enhancement. Solid component give typical heterogenous appearance on MRI, and peritumoral T2 hyperintensity is less compared to large their size. [9] In spite of the characteristic imaging features, they are usually confused for glioma, primitive neuroectodermal tumors (PNET), or ependymoma. [1],[3]
Histologically these tumors are characterized by perivascular pseudoressets throughout the tumor tissue more distinctly observed in solid areas of tumor. Most of the tumor cells are monotonous with coarse chromatin arrangement pattern. These rossets were characterized by short and thick blunt ended foot plates of astroblastoma cells directed toward the central blood vessel. These pseudorossets are also observed in glioblastoma and anaplastic astrocytoma, but appearance remains focal, while in astroblastoma these are spread all over the tumor tissue. Ependymoma also can have pseudorossets, but arrangement of cells remains more compact and cytoplasmic processes are thin, tapering toward central vessel and often fibrillated compared to thick and blunt ended in astroblastoma cells. Blood vessels in tumor tissue show areas of hyalinization. Some non-neural tumors also show the presence of pseudorossets, but they can be excluded on immunohistochemical demonstration of GFAP. [5],[6],[10],[11] In view of the unequivocal histological findings, MRI may play a crucial role in establishing a diagnosis. Even in our case, a final histological report of astroblastoma was given based on the unique imaging findings of the case.
Surgical excision of the tumor remains the mainstay of the treatment, which achieves decompression of tumor relieving raised intracranial pressure and decreases the cellular load. As these tumors generally present with raised intracranial pressure, role of surgery as a primary therapy is well justified. [1],[2],[3] In postoperative period, chemotherapy and radiotherapy have been tried in different series with limited success. [3],[5],[12] The overall prognosis of this tumor remains average with average survival being 4 years after the diagnosis in several series. [3],[5],[7],[12],[13] In some patients, chemotherapy with methotrexate, vincristine, and leukovarin have been tried successfully. [5] The present consensus is to do surgical excision of the patients with postoperative radiotherapy and chemotherapy with the grade of excision being the major determinant of prognosis. [13]
Astroblastomas on MRI are seen to characteristically appear as large lobulated heterogenously enhancing solid-cystic masses extending from the peripheral cortex to the periventricular region with the solid portion appearing isointense to grey matter on T2 weighted images. In view of the difficulty in differentiating these tumors from ependymomas on histology, we recommend that the absence or presence of these imaging be used for preparing the histopathology reports in patients with suspected astroblastomas.
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[Figure 1], [Figure 2A], [Figure 2B], [Figure 2C], [Figure 2D]
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