Rare histological variants in ependymomas: histopathological analysis of 13 cases.

Ependymomas are rare brain tumors representing about 3% of all intra-cerebral and spinal neoplasms. The WHO classification recognizes various rare histological ependymoma variants (i.e., lipidized ependymoma, giant cell ependymoma, etc.). However, a detailed analysis of a larger series of such cases is still lacking. We analyzed 13 case of ependymoma presenting unusual histological features. The data analysis of our series and its comparison to the cases published in literature did not reveal any close association between these features and the clinical parameters (such as age or localization). Moreover, some of these features can be found combined in individual tumors, suggesting that these variants may represent a spectrum of differentiation rather than true specific entities. However, awareness on these rare histological patterns in ependymomas is necessary in the differential diagnosis with other primary or secondary brain tumors.