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  • Updated 03.10.2022
  • Released 08.08.1994
  • Expires For CME 03.10.2025

Ependymoma

Introduction

Overview

Ependymomas are one of the more common childhood brain tumors. Total resection improves the likelihood of survival 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.

Key points

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 (08). 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 (52). 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 historically include cellular ependymoma, papillary ependymoma, and ZFTA-fusion positive ependymoma. The latter is a new entity, incorporating molecular aspects into classification for the first time (53; 72).

The 2021 WHO Classification of CNS Tumors further separates ependymomas by molecular features, including methylation characteristics, while still maintaining tumor location as a defining factor (54). Notably, supratentorial RELA tumors are now designated as ZFTA (a newer designation for C11orf95 as it has more fusion partners than RELA) and are separated from those supratentorial ependymomas with YAP1 fusion. Posterior fossa ependymomas are group PFA or PFB tumors. Anaplasia is not part of classification, and the designations clear cell, papillary, and tanycytic are no longer used. Subtypes included are:

• Supratentorial ependymoma

• Supratentorial ependymoma, ZFTA fusion-positive

• Supratentorial ependymoma, YAP1 fusion-positive

• Posterior fossa ependymoma

• Posterior fossa ependymoma, group PFA

• Posterior fossa ependymoma, group PFB

• Spinal ependymoma

• Spinal ependymoma, MYCN-amplified

• Myxopapillary ependymoma

• Subependymoma

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 (44).

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