脳表部Clear Cell Ependymomaの1例

Brain Surface Clear Cell Ependymoma : case report

I．はじめに

　Ependymomaは通常，脳室周囲のependymalcellもしくはsubependymal cellから発生すると考えられている^2,7,8,10）．通常脳室周囲に存在するが，テント上の例は脳実質内に発育する傾向があるといわれている^9）．しかし，脳表に露出して存在することは非常に稀である^4）．今回われわれは脳表に存在し，大きな嚢胞を伴ったclear cellependymomaを経験したので，その病理所見，発生起源について若干の考察を加え報告する．

We report a case of brain surface clear cell ependymoma. A 13-year-old boy presented with complaintsof right hypesthesia. Computed tomography and magnetic resonance image showed a left fronto-parietalcystic, calcified mass lesion. He underwent total resection of the tumor including cyst wall. The tumor lo-cated on the surface of the parietal lobe was sharply demarcated from the surrounding brain tissue andthere was no continuity with the ventricular wall. Histological examination of the surgical specimensshowed oligoclendroglioma-like cells that had round unclei, clear cytoplasm which formed perivascularpseudorosettes, and immunoreactivity for glial fibrillary acidic protein (GFAP). Electromicroscopically,microvilli were seen. The findings were compatible with clear cell ependymoma. The cyst wall was linedwith a layer of single cuboidal cells and, immunohistochemically, had no basal membrane. The inner sur-face of the cyst was positive for EMA, and the cuboidal cells were positive for GFAP. We discuss possiblemechanisms for tumor growth in our case and the histogenesis of its cyst.