Pilocytic astrocytoma

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Pilocytic_astrocytoma]]

General

  • Low-grade astrocytoma - WHO Grade I by definition.
  • Classically in the cerebellum in children; most common glioma in children.[1]
  • The optic glioma associated with neurofibromatosis 1.

Gross

Features:[1]

  • Usually well-circumscribed.
  • Cystic or solid.
  • Do not smear. (Ref. ?)

Microscopic

Features:[2]

  • Classically biphasic (though either may be absent):
    1. Fibrillar.
    2. Microcystic/loose.
  • Hair-like fibres ~ 1 micrometer; pilo- = hair.[3]
    • Best seen on smear or with GFAP IHC.
  • Rosenthal fibres - key feature.
    • May be rare. Not pathognomonic (see below).
  • Eosinophilic granular bodies.
  • Low cellularity - when compared to medulloblastoma and ependymoma.

Notes:

  • +/-Microvascular proliferation.
  • +/-Focal necrosis.
    • Necrosis with pseudopalisading more likely glioblastoma.
  • +/-Mitoses - not significant in the context of the Dx.

DDx (of Rosenthal fibers):[4]

  • Chronic reactive gliosis.
  • Subependymoma.
  • Ganglioma.
  • Alexander's disease (rare leukodystrophy).

DDx of pilocystic astrocytoma (brief):

  • Piloid gliosis.
  • Oligodendroglioma.
  • Glioblastoma (uncommon - but important).

Images

Stains

  • PAS-D: eosinophilic granular bodies +ve.

IHC

Features:[6]

  • GFAP +ve (fibres).
  • CD68: may have a significant macrophage component.
  • KI-67: may be "high" (~20% ???).

See also

References

  1. 1.0 1.1 Perry, Arie; Brat, Daniel J. (2010). Practical Surgical Neuropathology: A Diagnostic Approach: A Volume in the Pattern Recognition series (1st ed.). Churchill Livingstone. pp. 82. ISBN 978-0443069826.
  2. Perry, Arie; Brat, Daniel J. (2010). Practical Surgical Neuropathology: A Diagnostic Approach: A Volume in the Pattern Recognition series (1st ed.). Churchill Livingstone. pp. 82-4. ISBN 978-0443069826.
  3. URL: http://dictionary.reference.com/browse/pilo-. Accessed on: 24 November 2010.
  4. MUN. 9 Mar 2009.
  5. URL: http://path.upmc.edu/cases/case195.html. Accessed on: 8 January 2012.
  6. Perry, Arie; Brat, Daniel J. (2010). Practical Surgical Neuropathology: A Diagnostic Approach: A Volume in the Pattern Recognition series (1st ed.). Churchill Livingstone. pp. 84. ISBN 978-0443069826.