CNS tumor
Ependymal tumors
Ependymoma

Author: Eman Abdelzaher, M.D., Ph.D. (see Authors page)

Revised: 30 August 2017, last major update August 2012

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Ependymoma [title] CNS

See also: CellularClear cellPapillaryTanycyticOther
Cite this page: Abdelzaher, E. Ependymoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/cnstumorependymoma.html. Accessed October 22nd, 2017.
Definition / general
  • Slowly growing tumor of ependymal cells arising from walls of ventricles or spinal canal
  • Exhibit glial (GFAP+) and epithelial (EMA+) differentiation
Epidemiology
  • 3 - 9% of primary CNS tumors
  • More common in children / young adults but all age groups are affected (1 month - 81 years)
  • Infratentorial ependymomas more common in children; cause hydrocephalus from obstruction if in posterior fossa
  • Spinal tumours more common in adults (30 - 40 years); better able to excise completely and generally better prognosis at this site
  • Supratentorial ependymomas affect both children and adults
  • No gender predilection
Sites
  • Arise in ventricles (lined by ependyma) in cerebrum or brainstem, including spinal cord remnant of central canal
Grading
  • WHO grade II
Radiology description
Neuroimaging:
  • Well circumscribed lesions with variable enhancement
  • May have cystic change (especially in supratentorial tumours), hemorrhage, calcification
Radiology images

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MRI: Ependymoma of fourth ventricle

Prognostic factors
  • Poor prognosis due to CSF dissemination (average survival 4 years with surgery and radiation) and inability to excise completely (near pontine and medullary nuclei)
  • Poor prognostic factors are radiologic residual disease after surgery; higher Ki67 indices ( > 20.5%, Am J Surg Pathol 2004;28:914)
  • Poor prognostic factors for pediatric intracranial tumors are:
    • Subtotal resection with p53+ or MIB+ > 5% or
    • Complete resection with MIB > 15% in hypercellular areas (Mod Pathol 2003;16:980)
Case reports
Treatment
  • Gross total removal, often difficult
Gross description
  • Soft tan masses
  • May have discrete margin from surrounding brain or spinal cord
  • Grows exophytically into fourth ventricle
  • Ependymomas can fill fourth ventricle and exit out through foramina of Luschka or Magendie (called plastic ependymomas)
Gross images

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Arising from floor of fourth ventricle

Microscopic (histologic) description
  • Ependymomas have discrete interface with surrounding parenchyma
  • Moderately cellular, composed of monomorphic cells with round / oval nuclei and salt and pepper chromatin
  • No / rare mitoses are rare
  • Key histological features are perivascular pseudorosettes and ependymal rosettes
  • Other features include: areas of fibrillarity, regressive changes (myxoid degeneration, hemorrhage, calcifications, hyalinized vessels)
  • Variable nonpalisading necrosis

Ependymal rosettes and ependymal canals:
  • Composed of columnar cells arranged around a central lumen
  • Lumen may be round or oval, does not have a hypereosinophilic border
  • True rosettes are diagnostic of ependymoma but not always present

Perivascular (pseudo) rosettes:
  • Ependymal cell processes directed towards vessel wall, processes become thinner as they extend around blood vessel with formation of perivascular anuclear zones of GFAP+ fibrillary processes
  • More common than ependymal rosettes in ependymoma but also present in glioma
Microscopic (histologic) images

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Rosettes and pseudorosettes

Pigmented tumor

GFAP

Positive stains
  • GFAP, S100, vimentin
  • EMA (positive along luminal surface of ependymal rosettes or as dot-like cytoplasmic vacuoles representing microlumens)
  • Rarely cytokeratin
Negative stains
  • Most neuronal antigens; no reticulin or type IV staining fibrils in ependymoma aggregates
Electron microscopy description
  • EM is necessary to differentiate ependymoma from glioma if rosettes not present
  • Ependymoma has perivascular rosettes, abnormal cilia, intracytoplasmic lumina with variable microvilli and cilia, basal bodies, microvillous inclusions; perinuclear intracytoplasmic intermediate filaments, long junctional complexes
  • No basement membrane found in aggregated ependymoma cells
Electron microscopy images

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Electron dense bodies

Molecular / cytogenetics description
  • #22 deletions in 30 - 70%; inactivation of NF2 or loss of expression of protein in 29 - 38% of spinal tumors
  • Alterations in protein 4.1 family members is common
  • Loss of protein 4.1B and 4.1R deletions more common in childhood, intracranial and anaplastic tumors
  • Protein 4.1G deletions associated with more aggressive disease (Mod Pathol 2005;18:991, Mod Pathol 2002;15:526)
Differential diagnosis
  • Glioma: no true rosettes, no cell - cell junctions, no intracytoplasmic microvilli lined lumina