Ependymoma

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  • i. Types:
    • 1. ependymoma (cellular, papillary, clear cell) (childhood tumor)
    • 2. anaplastic ependymoma
    • 3. myxopapillary ependymoma (spinal neoplasm in adulthood) – has mucinouss material that accumulates about a hyalinized vessel wall
    • 4. subependymoma
  • ii. account for 30% of CNS neoplasms in children < 3 years
  • iii. formed of uniform cells with indistinct cytoplasmic borders and round nuclei
    • 1. also see pseudorosette which is a perivascular anuclear zone of fibrillary processes that taper towards a vessel; pseudorosettes are the hallmark of the ependymoma but ependymal rosettes with a central lumen and a halo of neopastic cells may also be found but less consistently
    • 2. blepharoplasts are commonly seen (aborted tufts of cilia) in the apical cytoplasm
  • iv. genetically often see loss of chromosome 22; Remember: NF2 and ependymoma (22) and NF1 and medulloblastoma (17)
  • v. slow growing tumors that are often cystic; calcification is common
  • vi. arise from the floor or roof and protrude through the outlet foramina into the adjacent CSF cisterns but may also arise from the cerebellar hemisphere; 60% are found in the posterior fossa
  • vii. 5 year survival rate for infratentorial ependymomas in childhood is 45%
  • viii. angiography may show hypovascular mass to extremely hypervascular; CT shows most ependymomas to be isodense with around 50% being calcified, mild to moderate enhancement is seen in 70%
  • ix. MRI classically shows lobulated soft tissue mass that forms a cast or mold of the fourth ventricle and extrudes through its outlet foramina into adjacent subarachnoid cisterns
    • 1. solid component is hypo or isointense to brain on T1 and hyperintense on T2 weighted scans with heterogeneity with contrast due to calcification, vascularity or blood degradation products
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