Ependymoma RELA fusion-positive

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Ependymoma RELA fusion-positive is a recently accepted molecular variant of ependymoma, only recognized in the 2016 update to the WHO classification of CNS tumors. They are the most common type of supratentorial ependymoma in children, and not found in the posterior fossa or spinal cord.

Epidemiology

RELA fusion-positive tumors account for 70% of childhood supratentorial ependymomas, and a smaller number of supratentorial tumors in adults . They have a M:F ratio of 2:1 .

Pathology

These tumors can be both grade II or III and demonstrate a variety of histological morphologies, although clear cells and prominent vascularity are common . The presence of the RELA fusion gene can be assessed with FISH.

Immunophenotype
  • GFAP positive
  • EMA positive
  • L1CAM positive
    • correlates closely with the presence of RELA fusion
    • not exclusive to ependymomas

Treatment and prognosis

Unlike the less common other supratentorial molecular subtype of ependyma (YAP1 fusion), RELA fusion-positive tumors have a poor prognosis .