Pilocytic astrocytoma

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Pilocytic astrocytoma
Diagnosis in short

Pilocytic astrocytoma. Smear. H&E stain.
LM DDx piloid gliosis, oligodendroglioma, glioblastoma
Stains PAS-D +ve (eosinophilic granular bodies)
IHC GFAP +ve
Gross usually cerebellar +/-cystic
Site brain - usu. cerebellum
Prevalence common - esp. in children
Prognosis good (WHO Grade I)

Pilocytic astrocytoma, abbreviated PA, is a low-grade astrocytoma. It the most common glioma in children.

General

Imaging

  • Well-defined, T2-hyperintense.
  • Strong CM enhancement.
  • May contain cysts.
  • Associated with midline structures.

Gross

Features:[1]

  • Usually well-circumscribed, soft.
  • Can be cystic with mural nodule.
  • Optic gliomas may present as fusiform mass.
  • Occ. calcium deposits and hemosiderin.

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.
  • Ganglioglioma.
  • Alexander's disease (rare leukodystrophy).

DDx of pilocystic astrocytoma (brief):

Images

Smears

  • Bipolar cells with hair-like processes - smear - very high mag. (WC)

  • EGBs - smear. (WC/AFIP)

  • Rosenthal fibres - smear. (WC/AFIP)

Sections

  • Rosenthal fibres. (WC)

  • Occasional pleomorphism. (WC)

  • Microvascular proliferation. (WC)

www:

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% ???).
  • Olig 2: Usually strongly present.[7]

Molecular

  • Almost all alteration associated with the MAPK pathway.[8]
  • KIAA1549-BRAF fusion transcripts most common in sporadic PA (up to 2/3 of all cases).
    • DDx: Fusion reported in rare Diffuse Leptomeingeal Glioneuronal Tumors and Oligodendroglioma.
  • Rarely BRAF, KRAS or FGFR1 mutations, NTRK2, SRGAP3-RAF1 or FAM131B-BRAF fusions.[9][10]
  • Up to 15% of all NF1 patients develop a PA ("optic glioma" as predilection).[11]
  • Rare reports of PA in Noonan-Syndrome (PTPN11 mutation).[12]

Prognosis

  • Excellent (10-year OS: 90%)
  • In thalamic/chiasmatic region not so good (incomplete resection, often Pilomyxoid astrocytoma).
  • Primary treatment: surgery. Incomplete resection: RT has to be considered.
    • Chx is given in rare cases that are still progredient[13]

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. ↑ Munoz D. 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.
  7. ↑ Otero, JJ.; Rowitch, D.; Vandenberg, S. (Sep 2011). "OLIG2 is differentially expressed in pediatric astrocytic and in ependymal neoplasms.". J Neurooncol 104 (2): 423-38. doi:10.1007/s11060-010-0509-x. PMID 21193945.
  8. ↑ Collins, VP.; Jones, DT.; Giannini, C. (Jun 2015). "Pilocytic astrocytoma: pathology, molecular mechanisms and markers.". Acta Neuropathol 129 (6): 775-88. doi:10.1007/s00401-015-1410-7. PMID 25792358.
  9. ↑ Jones, DT.; Hutter, B.; Jäger, N.; Korshunov, A.; Kool, M.; Warnatz, HJ.; Zichner, T.; Lambert, SR. et al. (Aug 2013). "Recurrent somatic alterations of FGFR1 and NTRK2 in pilocytic astrocytoma.". Nat Genet 45 (8): 927-32. doi:10.1038/ng.2682. PMID 23817572.
  10. ↑ Cin, H.; Meyer, C.; Herr, R.; Janzarik, WG.; Lambert, S.; Jones, DT.; Jacob, K.; Benner, A. et al. (Jun 2011). "Oncogenic FAM131B-BRAF fusion resulting from 7q34 deletion comprises an alternative mechanism of MAPK pathway activation in pilocytic astrocytoma.". Acta Neuropathol 121 (6): 763-74. doi:10.1007/s00401-011-0817-z. PMID 21424530.
  11. ↑ Friedrich, RE.; Nuding, MA. (Aug 2016). "Optic Pathway Glioma and Cerebral Focal Abnormal Signal Intensity in Patients with Neurofibromatosis Type 1: Characteristics, Treatment Choices and Follow-up in 134 Affected Individuals and a Brief Review of the Literature.". Anticancer Res 36 (8): 4095-121. PMID 27466519.
  12. ↑ Jones, DT.; Hutter, B.; Jäger, N.; Korshunov, A.; Kool, M.; Warnatz, HJ.; Zichner, T.; Lambert, SR. et al. (Aug 2013). "Recurrent somatic alterations of FGFR1 and NTRK2 in pilocytic astrocytoma.". Nat Genet 45 (8): 927-32. doi:10.1038/ng.2682. PMID 23817572.
  13. ↑ Metts, RD.; Bartynski, W.; Welsh, CT.; Kinsman, S.; Bredlau, AL. (Mar 2017). "Bevacizumab Therapy for Pilomyxoid Astrocytoma.". J Pediatr Hematol Oncol. doi:10.1097/MPH.0000000000000824. PMID 28338567.
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