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Tumor histology

There are two proposed cellular origins for ependymal tumors. These tumors may develop from:

  • Ependymal central neuroepithelial cells during embryogenesis
  • Malignant degeneration of mature ependymal cells in the ventricular linings of subependymal zones of cellular proliferation.

Mature ependymal cells involved. Perivascular pseudorosettes and true ependymal rosettes are characteristic.

  • Glial features lead to fibrillary appearance of the tumor.
  • Glial fibrillary acidic protein (GFAP) expression is common.
  • In general, tumor cells are polygonal with large nuclei, clumped chromatin, small but distinct nucleoli and cytoplasm which extend into processes.

Roughly one third of this tumors are high grade (anaplastic ependymoma):

  • Brisk mitotic activity and vascular proliferation seen
  • Associated with a worse prognosis


Summary of Histological Features of Ependymomas:

  • Arise within or adjacent to the ependymal lining of the ventricular system or central canal of the spinal cord.
  • Infratentorial ependymomas commonest in children.
  • Spinal cord ependymomas usually occur in adults.
  • Supratentorial ependymomas can occur in pediatric as well as adult patients
Macroscopic Appearance
  • Well-demarcated
  • Soft grey-red tumors
  • May be extensively cystic
  • Calcifications
Microscopic Appearance
  • Well-delineated
  • Moderately cellular tumor
  • Polygonal cells
  • Nuclei are generally uniform, moderately hyperchromatic and vary from round to oval
  • Nucleoli are small but distinct.
  • Cilia and blepharoblasts.
  • Perivascular pseudorosettes.
  • True ependymal rosettes
  • Anaplastic features (little consensus on definition of reliable histopathological indicators of anaplasia).
  • High cellularity, brisk mitotic activity, vascular proliferation and loss of perivascular rosettes (image 1)
Characteristic diagnostic feature

1. Anaplasia X200 - Anaplastic ependymoma with brisk mitotic activity and vascular proliferation.

2. Pseudorosettes X100 - Ependymoma with typical pseudorosettes characterized by nuclear free spaces around blood vessels.

3. Ependymal rosettes X200 - Ependymal rosettes.

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