Ependymoma

Ependymoma is a neuropathology tumour.

General

• Called the forgotten glial tumour.

Epidemiology:

• Usual site:
  • Adults: usu. spinal cord.
  • Children: usu. posterior fossa.
• May be assoc. with neurofibromatosis 2.

There are four main ependymal tumors:

1. Ependymoma (not otherwise specified).
   • Other flavours:
     • Cellular ependymoma.
     • Papillary ependymoma.
     • Clear cell ependymoma.
     • Tanycytic ependymoma.
2. Anaplastic ependymoma.
3. Myxopapillary ependymoma.
   • Classically at filum terminale.
4. Subependymoma
   • Typically seen in IVth ventricle

Microscopic

Classic ependymoma

Features:

• Cells have a "tadpole-like" morphology.
  • May also be described as ice cream cone-shaped.
• Rosettes = circular nuclear free zones/cells arranged in a pseudoglandular fashion; comes in two flavours in ependymoma:
  • Perivascular pseudorosettes = (tumour) cells arranged around a blood vessel; nuclei of cells distant from the blood vessel, i.e. rim of cytoplasm (from tumour cells) surround blood vessel (nucleus-free zone); more common than ependymal rosette... but less specific.
  • Ependymal rosette (AKA true ependymal rosette) = rosette has an empty space at the centre - key feature.
• Nuclear features monotonous, i.e. "boring".
  • There is little variation in size, shape and staining.

DDx (classic ependymoma):

• Subependymoma.
• Glioblastoma (GBM).
  • Invasive border = GBM; circumscribed border of lesion = ependymoma.

Images

www:

• Ependymoma (flickr.com).
• Ependymoma - ependymal rosettes (ajnr.org).
• Anaplastic ependymoma - case 1 (upmc.edu).
• Anaplastic ependymoma - case 2 (upmc.edu).

• 

  Ependymoma - intermed. mag. (WC)

• 

  Ependymoma - low mag. (WC)

Myxopapillary ependymoma

Features:

• Perivascular pseudorosettes:
  • Myxoid material surround blood vessels.
    • Myxoid material surrounded by tumour cells.

Images:

• Myxopapillary ependymoma - high mag. (WC).
• Myxopapillary ependymoma (bmj.com) - part of careers.bmj.com article on paediatric pathology.
• Myxopapillary ependymoma - cytology (WC).
• Myxopapillary ependymoma - several images (upmc.edu).

Grading

Easy:

• Subependymoma = WHO grade I.
• Myxopapillary ependymoma = WHO grade I.

Not-so-easy:

• Classic ependymoma = WHO grade II.
• Anaplastic ependymoma = WHO grade III.

Grade II vs. Grade III:

• Cellular density.
• Mitoses.
• Necrosis.
• Microvascular proliferation.

Notes:

• Many tumours fall between grade II and grade III. These are called "indeterminate" by many.

IHC

• Reticulin.
• GFAP.
• MIB1.

See also

• Neuropathology tumours.