This article includes discussion of ependymoma, benign ependymomas, clear cell ependymomas, malignant ependymomas, anaplastic ependymomas, myxopapillary ependymomas, subependymomas, and ependymomas. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.
Ependymomas are one of the more common childhood brain tumors. After total resection, outcome is excellent. However, for patients whose tumors are subtotally resected or anaplastic, disease relapse is common. The author summarizes the outcomes of new treatment approaches and the value of adjuvant chemotherapy. Increased biological understandings have already changed classification and have altered management of the tumor. They have clearly demonstrated that pediatric supratentorial and infratentorial ependymomas are different entities.
Historical note and terminology
Ependymomas were first described by Bailey in 1924. Initial classification schema using light microscopy findings subdivided ependymomas into epithelial, myxopapillary, and cellular types (07). Because of the variable relationship demonstrated between histological findings and outcome in different subgroupings of ependymomas, other classification schemas have been proposed.
The most recent World Health Organization classification of CNS tumors defines ependymoma as a tumor composed predominantly of neoplastic ependymal cells (51). This classification system distinguishes ependymoma WHO grade II from anaplastic or malignant ependymoma, WHO grade III. Myxopapillary ependymomas are considered a distinct variant of ependymoma occurring almost exclusively in the region of the cauda equina (WHO grade I). Subclassifications of ependymoma include cellular ependymoma, papillary ependymoma, and RELA-fusion positive ependymoma. The latter is a new entity, incorporating molecular aspects into classification for the first time (52). It is likely that further molecularly based subclassification will be utilized in the future (69). Subependymomas are nodular tumors that are thought to have a different, more benign prognosis than other types of ependymomas that occur in the brain.
Ependymoblastoma was initially considered a subtype of ependymoma. Histologically, ependymoblastomas are primarily composed of small, undifferentiated cells associated with regions of relatively well-formed ependymal blastic rosettes. The tumor is now classified as an embryonal tumor and is primarily considered a subtype of primitive neuroectodermal tumor of childhood. In the revised World Health Organization classification of CNS tumors, ependymoblastomas are given a separate designation under the general category of embryonal tumors. Others do not even consider ependymomas a distinct entity (43).