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A Meningioma in the Posterior Fossa without Dural Attachment: Case report Shigehiro NAKAHARA 1 , Kaoru YOSHINO 1 , Yuzuru HASEGAWA 1 , Satoshi TANI 1 , Robert Tomohiko NUMOTO 2 , Junichi TANAKA 2 1Department of Neurosurgery, The Jikei University School of Medicine 2Division of Neuropathology, The Jikei University School of Medicine Keyword: Meningioma , Posterior fossa , Dural attachment , Histological findings pp.849-852
Published Date 1993/9/10
DOI https://doi.org/10.11477/mf.1436900711
  • Abstract
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An extremely rare case of a meningioma in the pos-terior fossa without dural attachment has been reported. The patient was a 56-year-old male whose chief man-ifestation was the abnormality of his CT scan. His past history included gastric and colonic polyp when he was 54, 55 years old, and non-Hodgkin's lymphoma before hospitalization in our department. CT scan showed a small round non-enhancing lesion located at the lateral site of the right cerebellar cortex. T1 weighted image of MRI showed a homogenous low intensity lesion with partial enhancing with Gd-DTPA.Proton image showed a remarkable low intensity lesion which showed an extramedullary mass. Right retromastoid craniec-tomy was performed. The mass was an extramedullary tumor which had no relation with the cerebellar cortex and dura matter. The arachnoid membrane around the tumor was intact. The tumor was totally resectecl and the patient had no neurological deficits.

Histopathologically, the tumor was delineated into laminar structures by collagen fiber. Tumor cells were spindle in shape and made a whorling formation. There was no psammoma body and it had a hyperchromatic nuclei without mitotic features. Electron microscopic stu-dies revealed no typical interdigitation but irregularity of the cell membrane. Abundant collagen fibers were in contact with basement membrane of the tumor. Accord-ing to these findings, we diagnosed fibroblastic menin-gioma with atypical forms.

Meningiomas without dural attachment are rare in adults, especially extremely rare of the posterior fossa. There are only 23 previous reports of “meningioma of the posterior fossa without dural attachment”. Cantore divided these meningiomas into three groups (IV ventri-cle, inferior tela choroidea and cisterna magna). Our pre-sent case had no attachment to the dura mater and chor-oid plexus of IV ventricle.

We consider that this meningioma occurred in the col-lagen fiber mass or arose from the ectopic dural sinus with abundant collagen fibers which revealed no dural attachment and showed an atypical MR image of meningioma.

We conclude that our case falls under another cate-gory, that of meningioma of the posterior fossa without dural attachment.


Copyright © 1993, Igaku-Shoin Ltd. All rights reserved.

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電子版ISSN 1882-1251 印刷版ISSN 0301-2603 医学書院

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