Neuropathology: Practice Question

Which of the following occurs mainly in infants, has loss of H3K27me3 expression by IHC, and has EZHIP overexpression?
  1. RELA fusion-positive ependymoma
  2. Supratentorial ependymoma
  3. Spinal cord ependymoma
  4. Posterior fossa ependymoma, group A
  5. Posterior fossa ependymoma, group B
Show Answer and Explanations

RELA fusion-positive ependymoma

Incorrect. RELA fusion-positive ependymomas are the older classification for supratentorial ependymoma with mutations of the ZFTA genes.

Supratentorial ependymoma

Incorrect. Supratentorial ependymomas are associated with mutations of the ZFTA genes, or YAP-1 fusions, or neither, in which case they would be described histologically.

Spinal cord ependymoma

Incorrect. Spinal cord ependymomas are classified by the presence or absence of MYCN–amplification. MYCN-amplified ependymoma is mostly in adults and has anaplastic histology. They are usually found in the cervical or thoracic spinal cord. These spinal cord tumors are heterogeneously T2-hyperintense and enhancing and are usually extramedullary, or have an exophytic portion if intramedullary. These have a poor prognosis with early dissemination.

Posterior fossa ependymoma, group A — Correct answer

Correct. Posterior fossa ependymoma, group A are found mostly in infants, have the loss of H3K27me3 expression by IHC, have EZHIP overexpression, and a worse prognosis than type B tumors. They are more likely to be lateral and have cerebellar invasion.

Posterior fossa ependymoma, group B

Incorrect. Group-B posterior fossa ependymomas are more common in adults and older children. On imaging they appear as a lobulated, heterogeneous mass in the body or inferior fourth ventricle, often extending through the foramen of Magendie into the cisterna magna or through the foramina of Luschka into the cerebellopontine angle cisterns. Cystic changes and calcification are frequent.

Summary

Summary: Ependymoma is classified by location (spinal, supratentorial, posterior fossa). The posterior fossa tumors are divided into groups A and B. Posterior fossa ependymoma, group A are found mostly in infants, have the loss of H3K27me3 expression by IHC, have EZHIP overexpression, and a worse prognosis than type B tumors. They are more likely to be lateral and have cerebellar invasion.
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