Pilocytic astrocytoma
Pilocytic astrocytoma, abbreviated PA, is a low-grade astrocytoma. It the most common glioma in children.
| 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) |
General
- Low-grade astrocytoma - WHO Grade I by definition, but rare anaplastic forms have been described.
- Classically in the cerebellum in children; most common glioma in children.[1]
- The optic glioma is associated with neurofibromatosis 1.
- Rare variants include Pilomyxoid astrocytoma and Anaplastic pilocytic astrocytoma.
Imaging
- Well-defined, T2-hyperintense.
- Strong CM enhancement.
- May contain cysts.
- Associated with midline structures.
Gross
Features:[1]
- Usually well-circumscribed.
- Often cystic with mural nodule.
Microscopic
Features:[2]
- Classically biphasic (though either may be absent):
- Fibrillar.
- 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):
- Piloid gliosis (esp. in sellar lesions).
- Oligodendroglioma.
- Glioblastoma (uncommon - but important).
- Tanycytic Ependymoma
- Pilocytic tumor components may be found in Ganglioglioma, DNET, RGNT
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]
See also
References
- ↑ 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.
- ↑ 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.
- ↑ URL: http://dictionary.reference.com/browse/pilo-. Accessed on: 24 November 2010.
- ↑ Munoz D. 9 Mar 2009.
- ↑ URL: http://path.upmc.edu/cases/case195.html. Accessed on: 8 January 2012.
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ 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.