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Mixed astroblastoma–arteriovenous malformation complex: A case report

2017-01-12 17:11 著作人:苟医生

病文科 / 姚坤 李天富 朱明旺 段泽君 王计强 胡泽良 边宇 齐雪岭

An astroblastoma is a rare glial tumor accounting for 0.45-2.8% of braingliomas and occur in young adults with a predilection for the cerebralhemispheres. The coexistence of astroblastoma and arteriovenous malformation(AVM) in the brain has not been reported in the literature,hence this report.The potential role of the angiogenic factors that might have modulated theevolution of the neoplasm is discussed.

A 36-year-old man presented with a 6 day history of right frontotemporalheadache, nausea and vomiting and the headache has worsened for the past 3 days.Neurological examination revealed left homonymous hemianopia and neck rigidity.Cranial computed tomography (CT) scan revealed right occipital lobe hemorrhage[Figure 1a]. The CT-angiography and digital subtraction angiography revealedright posterior cerebral artery malformation associated with an aneurysm [Figure1b and c]. As the patient could not afford further studies and there wasclinical deterioration,he was taken up for the surgery. The pre-operativediagnosis was a vascular malformation with aneurysm involving the rightposterior cerebral artery and right occipital lobe hemorrhage. Patient underwentright parieto- occipital craniotomy,which revealed a highly hemorrhagic dark-redlesion in the temporo-occipital cortex with abnormal surrounding vessels. Thelesion was well-circumscribed pushing borders and it was completely resectedsurgically along with vascular malformation. The post-operative course wasuneventful. He did not receive post-operative radiotherapy. There was noevidence of tumor recurrence at the 5 month follow-up [Figure 1d]. The long-termfollow-up is in progress.

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Histological features of the tumor were consistent with astroblastoma,in thesame area,having abnormal and tortuously distributed vessels. We observed singleand multiple layers of tumor cells forming prominent pseudorosettes around bloodvessels,with short and thick cytoplasmic processes oriented toward central bloodvessels [Figure 2a-c]. The nuclei were generally round to oval in shape. Tumorvessels were thickened,but not hyalinized. Patchy hemorrhage was observed. Inthe same area,abnormal and tortuously vessels [Figure 2d and e] were withmarkedly variable caliber,irregularly thickened walls and fibromuscularhyperplasia of the media were seen [Figure 2d and e]. Some of the vesselsrevealed internal elastic lamina on the elastic fiber staining [Figure 2f].There was no appreciable mitotic activity in the tumor cells. Onimmunohistochemical analysis,the tumor cells showed diffuse strong positivityfor neuron specific enolase [Figure 2g],S-100 protein [Figure 2h], glialfibrillary acidic protein (GFAP) [Figure 2i], vascular endothelial growth factor(VEGF) [Figure 2j] and vimentin [Figure 2k]. However,they were negative forepithelial membrane antigen [Figure 2l],synaptophysin,neurofilament protein andpan-cytokeratin. The Ki-67 labeling index was less than 2% in the tumor.

It was a rare situation that the occurrence of two different lesions of thecentral nervous system such as a vascular malformation andastroblastoma,discovered at the same time and in the same location. Atoperation,a well-defined lesion with pushing borders was noted.

The most cases of astroblastoma were seen in children and young adults likein this case. The first report was by Bailey and Bucy in 1930. They believedthat astroblastoma originated from astroblasts, an intermediate stage betweenglioblasts and astrocytes. In a study using electron microscopy,it was proventhat tumor cells of astroblastoma are intermediate between astrocytes andependymal cells and thus,the possible presence of tanycytes is presented as theorigin of astroblastoma. Histopathology showed characteristic perivascularpseudorosettes. These differed from the perivascular pseudorosettes inependymoma, the astroblastoma rosettes having short and thick cytoplasmicprocesses. The cytoplasmic processes had blunt-ended foot plates and wereattached to the basal lamina of blood vessels. Tumor cells were stronglyimmunoreactive for S-100 protein,GFAP and vimentin and the extent ofhyalinization of blood vessels varied

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Figure 2: (a-c) Well-developed perivascular pseudorosettes are seen throughout the tumor (H and E, ×200, ×400, ×400). (d and e) abnormal, tortuously distributed vessels characteristic of an arteriovenous malformation aggregated with the tumor. (f) Elastic fiber stain. (g) Neuron specific enolase stain. (h) S-100 stain. (i) Glial fibrillary acidic protein stain. (j) Vascular endothelial growth factor stain. (k) Vimentin stain. (l) Epithelial membrane antigen stain from case to case. The histological characteristics in our patient support the diagnostic of astroblastoma.

Astroblastoma rarely infiltrates into the surrounding tissue,especially inlow-grade astroblastomas. This is an important characteristic to helpdistinguish the lesion from that of a fibrillary astrocytoma,which commonlyinfiltrates the nearby brain tissue. The lesion in this case was foundwell-circumscribed with pushing borders during the surgery. It enabled us toremove the lesion completely. Astroblastomas were classified into low- grade andhigh-grade according to histological findings. Low-grade astroblastomas includedastroblastomas with uniform perivascular arrangement of pseudorosettes, low tomoderate numbers of mitotic figures,minimal cellular atypia and predominantsclerosis of the vascular walls. High-grades astroblastoma showed cytologicatypia,compact cellularity,perivascular cells with high mitotic rates. In thispatient,the Ki-67 labeling index was lesser than 2% and there was no appreciablemitotic activity. Tumor cell atypia was minimal. All these characteristicssupported the diagnostic of low- grade astroblastoma.

In this case,the histology revealed atypical cells characteristic ofastroblastoma and in the same area, AVM. This observation led to the possibilitythat the vascular needs for astroblastoma growth were most likely partlysupplied by the AVM and that their concurrent finding in the same location inthe brain was probably determined by a common genetic and molecular basis.

AVM is usually described as abnormalities consisting of tangled masses oftortuous arteries,veins and abnormal connecting channels that apparently resultfrom the lack of development of the local capillary bed. However,the naturalhistory of AVM remained uncertain. AVM was thought to be congenital lesionresulting from abnormal vascular development and many authors thought AVM as anactive process with the ability to grow,regress and reappear. Vascularremodeling may be mediated by angiogenic factors such as VEGF. VEGF isresponsible for endothelial cell replication,migration,differentiation andsurvival. The expression of VEGF has been found to be high in the endotheliallayer and media of AVM vessels. We thought VEGF secreted by tumor cells bindedto endothelial cells and might activate neoangiogenesis. It appeared that VEGFmight be the possible underlying factor for the occurrence of both AVM andastroblastoma at the same site.

Because of the rarity of astroblastomas,there was no consensus regardingtheir optimal management. Some people suggested that the best clinical resultswere obtained after total or subtotal resection of the tumor,followed byradiotherapy. Adjuvant therapy is recommended for high-grade and recurrentcases. Others believe that total resection of these tumors should be atherapeutic goal since no recurrence of the tumor was found in the short-term.Good prognosis was almost associated with well-circumscribed tumors,which permittotal resection of tumor in all astroblastomas. This case was a low-gradeastroblastoma. Complete resection was possible in this patient because of therelatively clear border between the tumor and adjacent brain tissue. So,weadvised patient regular follow-up without adjuvant radiation. No recurrence wasnoted until the last follow-up of 5 months and the long-time of follow- up wasstill in progress.

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