Classification and controversies in pathology of ependymomas

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. Literature has been reviewed using PubMed with the following key words: ependymoma, +/- prognosis, +/- biomaker, +/- grading, +/- immunohistochemistry, +/- proliferative index. Grading controversy arises from elusive WHO features and individual characteristics of ependymomas including tumour location, tumour pattern/variant and variable expression of biomarkers. 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.