Ependymoma

Ependymomas represent a relatively broad group of glial tumors with ependymal differentiation. They often arise from or near the lining of the ventricles of the brain or the central canal of the spinal cord but also occur within the brain parenchyma. 

Terminology

The unqualified term "ependymoma" should be used somewhat carefully as the entities included in this term vary in the literature and clinical practice. Generally, it is best to be specific, using the terminology of the WHO classification (see below). The five tumors included under the heading of "ependymal tumors" vary greatly in location, demographics, imaging features, histology, molecular characteristics, treatment and prognosis. They are, therefore, best thought of and discussed as separate entities.

Epidemiology

Overall, ependymomas have a bimodal distribution, with peaks in childhood and again later in adulthood. The incidence of different tumor types and locations varies greatly, with posterior fossa ependymomas predominating in childhood and spinal ependymomas in adulthood ^20-21.

Classification

Ependymal tumors can occur anywhere within the neuraxis; however, the distribution, histology and molecular characteristics, including DNA methylation profiling, are fairly site-dependent. As such the 5th edition (2021) WHO classification divides ependymal tumors into five distinct entities; three based on location, further subdivided according to molecular characteristics, and two other specific entities ^11,13,15,18.

• posterior fossa ependymoma

  • posterior fossa group A (PFA) ependymoma

  • posterior fossa group B (PFB) ependymoma

• supratentorial ependymoma

  • supratentorial ependymoma, ZFTA fusion-positive

  • supratentorial ependymoma, YAP1 fusion-positive

• spinal ependymoma

  • spinal ependymoma, MYCN-amplified

• myxopapillary ependymoma

  • almost exclusively spinal, most commonly within or caudal to the conus medullaris

• subepenymoma

  • most commonly in the intracranial ventricles, but sometimes also in the spinal cord ¹⁸