稀な画像所見を呈し免疫染色が病理診断に有用であった小脳clear cell ependymomaの1例

Immunohistochemical Study is Helpful for the Diagnosis of Cerebellar Clear Cell Ependymoma with Atypical Radiological Findings -Case Report-

Ⅰ．はじめに

　Clear cell ependymoma（CCE）は脳室内Monro孔付近に発生することが多いとされ， ependymomaの1 variantである¹⁰⁾．しかし，ependymomaに特徴的な組織パターンであるrosetteを欠くこともあり，類円形核と明るい胞体を有する細胞が主体の腫瘍であるため，hematoxylin-eosin染色ではoligodendrogliomaやhemangioblastomaとの鑑別が困難な場合が多い^1,3,7)．今回，われわれは術前画像診断に苦慮し，免疫組織学的検討が有用であった小脳実質内のCCEを経験したので報告する．

A 67-year-old male presented with a clear cell ependymoma with symptoms of ataxic gait and dizziness. Magnetic resonance imaging showed a ring enhanced and circumscribed mass lesion with some cysts in the left cerebellar hemisphere,and the vertebral artery angiogram showed the vascurality of the tumor fed by both the left posterior inferior cerebellar artery and the left superior cerebellar artery mainly. They demonstrated suspicious finding of metastatic tumor,glioblastoma,or cystic meningioma. Surgery via the left suboccipital approach revealed a whitish and solid tumor,which was demarcated from the cerebellar parenchyma and had no continuity with the 4th ventricle. Total resection of the tumor was successfully performed. The hematoxilyn-eosin staining of the surgical specimen was similar to hemangioblastoma or oligodendroglioma,however,immunohistochemical findings for glial fibrillary acidic protein,vimentin,epithelial membrane antigen,and factorⅧ were compatible with clear cell ependymoma. The patient's postoperative course was uneventful,and his symptoms improved. Clear cell ependymoma is known as a variant of ependymoma,which is usually located at the foramen of Monro. We think that the immunohistochemical study is highly helpful for the diagnosis of the cerebellar tumor with atypical presentation such as our case.