CNS cytopathology

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CNS cytopathology is a subset of neuropathology and cytopathology.

An introduction to cytopathology is in the cytopathology article. Cerebrospinal (CSF) specimens are dealt with in a separate article called CSF cytopathology.


Smears (really squash preps) are common in neuropathology. Here are some tips for getting a good smear:

  1. Sampling is key -- choose 3-4 small pieces of tissue from different areas of the tissue (if there are different colours, get some of each).
  2. Keep pieces small (easier to smear).
  3. Avoid air drying (place into formal alcohol immediately upon smearing).

Basic approach

CNS cytology
Glial Non-glial
thin - cannot be seen at low
power (2.5x obj.), true cytoplasmic
thick - can be seen at low
power (2.5x obj.), artifact of smearing
Edge of cluster smooth/non-distinct sharp

Glial vs non-glial:

Gliosis vs. neoplasm:

  • Gliosis - uniform, pink
  • Astrocytoma - irregular, coarse clumps of pink fibrillary material

High grade vs. low-grade:

  • Markers of high grade glioma:
  1. Mitoses (can see these in smear)
  2. Necrosis (can also see in smears)


  • Crush artifact (in smear preparation) can mimic glial processes.
    • Crush artifact vs. real glial processes:
      • No glial processes run perpendicular to the direction of smear.
      • Glial processes may branch.
      • Crushed/elongated nuclei are present in artifactual processes.


Most meningiomas smear rather well, the only exception being ones that are densely fibrous.

  • Key features of meningioma smears:
  1. Single cells or small groups of epithelioid cells with distinct cytoplasmic 'flags' (cytoplasm usually abundant)
  2. Round nuclei with vesicular chromatin and unapparent or small nucleoli
  3. Visible actin striations / stress filaments in cells (seen as pink straight lines)

Metastatic carcinoma

Typically has a 'cannonball' appearance -- with small, highly cohesive clusters of epithelioid cells.

Metastatic melanoma

  • Occasionally large bi- or multinucleated cells
  • Discohesive cells
  • Large nucleoli
  • Pigmented tumor cells
  • Accompanied by tumor infiltrating lymphocytes

Metastatic lymphoma

  • Small round and blue cells

Glial tumors

  • Elongated cell processes
  • Cohesive growth
  • Often attached to vasculature

Things that don't smear well

Cohesive tumours:

Things that smear well

Dyscohesive tumours:

See also


  1. 1.0 1.1 URL: Accessed on: 2 November 2010.
  2. URL: Accessed on: 3 November 2010.
  3. 3.0 3.1 3.2 3.3 3.4 Weedman Molavi, Diana (2008). The Practice of Surgical Pathology: A Beginner's Guide to the Diagnostic Process (1st ed.). Springer. pp. 252. ISBN 978-0387744858.

External links