Papillary ependymoma: its differential diagnosis from choroid plexus papilloma

Papillary ependymoma is a rare variant of ependymoma and often gives rise to confusion with choroid plexus papilloma because of topographic, light microscopic and ultrastructural similarities. Here, we report two cases of papillary ependymomas regarding their unique clinicopathologic features and differential points from choroid plexus papilloma. Brain MRI revealed a large mass in the left lateral ventricle in one case and a 3cm sized mass in the pineal area and the 3rd ventricle in the other. Microscopically, the tumor was characterized by papillary and tubular structures. Immunohistochemically, the tumor cells in both cases expressed cytokeratins(CK22 and CAM 5.2) but did not express glial fibrillary acidic protein(GFAP), vimentin, epithelial membrane antigen, and S100 protein. This is a very unusual immunohistochemical feature for papillary ependymoma. Ultrastructurally, the tumor showed a mosaic pattern of tumor cells with frequent intercellular microrosettes having a few stubby microvilli, a few cilia and zonulae adherentes. The cytoplasmic processes were markedly reduced compared to conventional ependymoma. The cytoplasm did not contain intermediate filaments. Interestingly, the mitochondria showed abnormal features with a pleomorphic shape and abnormal cristae in both cases. These ultrastructural features enabled differentiation between papillary ependymoma and choroid plexus papilloma in addition to the light microscopic findings.

An Ependymoma in the 4th Ventricle: Report of 1 Case

Storch is credited as being the first to describe in 1899 what we call "ependymoma" today. And ependymomas were first set apart as a single group by Bailey in 1924. The literature up to the present contains numerous reports of tumors classified as "ependymoma". From 1 to 6 percent of all intracranial tumors are ependymomas. As the above, the tumors are very rare. The incidence is higher in those with large proportion of young patients and average age is approximately 20 years. About 40 percent of intracranial ependymomas are supratentorial and the remainders are infratentorial. We experienced a case of 4th ventricular ependymoma with subarachnoid hemorrhage. A 23 year old female was admitted to the hospital because of severe headache and frequent vomiting, who had been intermittently suffered from the headache for 8 months prior to admission. On admission, the neurologic examinations revealed irritable mentality, vomiting and papilledema, and xanthochromic CSF was identified on lumbar puncture. X-ray films of skull series showed evidence of increased ICP. A mass lesion was suspected in the posterior fossa on vertebral angiogram and brain C-T films revealed a mass lesion in the midline of the posterior fossa, slightly enhanced on contrast study and associated with hydrocephalus. Following Torkildsen's shunting procedure suboccipital craniectomy was performed, and we removed the tumor mass incompletely within the 4th ventricle. The pathologically microscopic finding was papillary ependymoma, grade II. Total neuraxis irradiation was applied for 6 weeks. The post-operative course was satisfactory.