Classification and controversies in pathology of ependymomas.

PURPOSE: Bailey and Cushing established ependymoma as a brain tumour entity in the first brain tumour classification (1926). Diagnosis of ependymomas is not subject to controversy as long as other tumours presenting ependymoma-like features have been ruled out. Grading conversely is a source of debate. Description of histological features establishing diagnosis and grading of ependymomas may help to better understand this controversy. METHODS: Literature has been reviewed using PubMed with the following key words: ependymoma, +/- prognosis, +/- biomaker, +/- grading, +/- immunohistochemistry, +/- proliferative index. RESULTS: Grading controversy arises from elusive WHO features and individual characteristics of ependymomas including tumour location, tumour pattern/variant and variable expression of biomarkers. CONCLUSION: There is a need for a grading scheme with a proven general ability to dissociate grades, and to predict individual clinical evolution. Only then will stratified and targeted therapeutics for ependymal tumours be possible