Pilocytic astrocytoma: Difference between revisions

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#redirect [[Neuropathology_tumours#Pilocytic_astrocytoma]]
{{ Infobox diagnosis
| Name      = {{PAGENAME}}
| Image      = Pilocytic_astrocytoma_-_smear_-_very_high_mag.jpg
| Width      =
| Caption    = Pilocytic astrocytoma. Smear. [[H&E stain]].
| Synonyms  =
| Micro      =
| Subtypes  =
| LMDDx      = piloid gliosis, [[oligodendroglioma]], [[glioblastoma]]
| Stains    = PAS-D +ve (eosinophilic granular bodies)
| IHC        = GFAP +ve
| EM        =
| Molecular  =
| IF        =
| Gross      = usually cerebellar +/-cystic
| Grossing  =
| Site      = brain - usu. [[cerebellum]]
| Assdx      =
| Syndromes  =
| Clinicalhx =
| Signs      =
| Symptoms  =
| Prevalence = common - esp. in children
| Bloodwork  =
| Rads      =
| Endoscopy  =
| Prognosis  = good (WHO Grade I)
| Other      =
| ClinDDx    =
| Tx        =
}}
'''Pilocytic astrocytoma''', abbreviated '''PA''', is a low-grade [[astrocytoma]]. It the most common glioma in children.
 
==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.<ref name=Ref_PSNP82>{{Ref PSNP|82}}</ref>
*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:<ref name=Ref_PSNP82>{{Ref PSNP|82}}</ref>
*Usually well-circumscribed, soft.
*Can be cystic with mural nodule.
*Optic gliomas may present as fusiform mass.
*Occ. calcium deposits and hemosiderin.
 
==Microscopic==
Features:<ref name=Ref_PSNP82-4>{{Ref PSNP|82-4}}</ref>
*Classically biphasic (though either may be absent):
*#Fibrillar.
*#Microcystic/loose.
*Hair-like fibres ~ 1 micrometer; ''pilo-'' = hair.<ref>URL: [http://dictionary.reference.com/browse/pilo- http://dictionary.reference.com/browse/pilo-]. Accessed on: 24 November 2010.</ref>
**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):<ref>Munoz D. 9 Mar 2009.</ref>
*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====
<gallery>
Image:Pilocytic_astrocytoma_-_smear_-_very_high_mag.jpg | Bipolar cells with hair-like processes - smear - very high mag. (WC)
Image:Pilocytic_Micro.jpg | EGBs - smear. (WC/AFIP)
Image:Rosenthal_fibers.jpg | Rosenthal fibres - smear. (WC/AFIP)
</gallery>
====Sections====
<gallery>
Image:Rosenthal_HE_40x.jpg | Rosenthal fibres. (WC)
Image:Pilocytic astrocytoma cell pleomorphism.jpg | Occasional pleomorphism. (WC)
Image:Pilocytic astrocytoma endothelial proliferations.jpg | Microvascular proliferation. (WC)
</gallery>
www:
*[http://moon.ouhsc.edu/kfung/jty1/neurotest/Q19-Ans.htm Rosenthal fibre (ouhsc.edu)].
*[http://path.upmc.edu/cases/case162.html Pilocytic astrocytoma (upmc.edu)].
*[http://path.upmc.edu/cases/case90.html Pilocytic astrocytoma - another case (upmc.edu)].
*[http://path.upmc.edu/cases/case195/images/figure3b.jpg Pilocytic astrocytoma - pennies on a plate (upmc.edu)].<ref>URL: [http://path.upmc.edu/cases/case195.html http://path.upmc.edu/cases/case195.html]. Accessed on: 8 January 2012.</ref>
*[http://path.upmc.edu/cases/case397.html Pilocytic astrocytoma (upmc.edu)].
 
==Stains==
*PAS-D: eosinophilic granular bodies +ve.
 
==IHC==
Features:<ref name=Ref_PSNP84>{{Ref PSNP|84}}</ref>
*GFAP +ve (fibres).
*CD68: may have a significant macrophage component.
*KI-67: may be "high" (~20% ???).
*Olig 2: Usually strongly present.<ref name=pmid21193945>{{Cite journal  | last1 = Otero | first1 = JJ. | last2 = Rowitch | first2 = D. | last3 = Vandenberg | first3 = S. | title = OLIG2 is differentially expressed in pediatric astrocytic and in ependymal neoplasms. | journal = J Neurooncol | volume = 104 | issue = 2 | pages = 423-38 | month = Sep | year = 2011 | doi = 10.1007/s11060-010-0509-x | PMID = 21193945 }}</ref>
*[[IDH1]] (R132H) -ve.
*[[H3F3A]] (K27M) -ve.
 
==Molecular==
* Almost all alteration associated with the MAPK pathway.<ref>{{Cite journal  | last1 = Collins | first1 = VP. | last2 = Jones | first2 = DT. | last3 = Giannini | first3 = C. | title = Pilocytic astrocytoma: pathology, molecular mechanisms and markers. | journal = Acta Neuropathol | volume = 129 | issue = 6 | pages = 775-88 | month = Jun | year = 2015 | doi = 10.1007/s00401-015-1410-7 | PMID = 25792358 }}</ref>
* 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.<ref>{{Cite journal  | last1 = Jones | first1 = DT. | last2 = Hutter | first2 = B. | last3 = Jäger | first3 = N. | last4 = Korshunov | first4 = A. | last5 = Kool | first5 = M. | last6 = Warnatz | first6 = HJ. | last7 = Zichner | first7 = T. | last8 = Lambert | first8 = SR. | last9 = Ryzhova | first9 = M. | title = Recurrent somatic alterations of FGFR1 and NTRK2 in pilocytic astrocytoma. | journal = Nat Genet | volume = 45 | issue = 8 | pages = 927-32 | month = Aug | year = 2013 | doi = 10.1038/ng.2682 | PMID = 23817572 }}</ref><ref>{{Cite journal  | last1 = Cin | first1 = H. | last2 = Meyer | first2 = C. | last3 = Herr | first3 = R. | last4 = Janzarik | first4 = WG. | last5 = Lambert | first5 = S. | last6 = Jones | first6 = DT. | last7 = Jacob | first7 = K. | last8 = Benner | first8 = A. | last9 = Witt | first9 = H. | title = Oncogenic FAM131B-BRAF fusion resulting from 7q34 deletion comprises an alternative mechanism of MAPK pathway activation in pilocytic astrocytoma. | journal = Acta Neuropathol | volume = 121 | issue = 6 | pages = 763-74 | month = Jun | year = 2011 | doi = 10.1007/s00401-011-0817-z | PMID = 21424530 }}</ref>
*Up to 15% of all [[NF1]] patients develop a PA ("optic glioma" as predilection).<ref>{{Cite journal  | last1 = Friedrich | first1 = RE. | last2 = Nuding | first2 = MA. | title = 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. | journal = Anticancer Res | volume = 36 | issue = 8 | pages = 4095-121 | month = Aug | year = 2016 | doi =  | PMID = 27466519 }}</ref>
*Rare reports of PA in Noonan-Syndrome (PTPN11 mutation).<ref>{{Cite journal  | last1 = Jones | first1 = DT. | last2 = Hutter | first2 = B. | last3 = Jäger | first3 = N. | last4 = Korshunov | first4 = A. | last5 = Kool | first5 = M. | last6 = Warnatz | first6 = HJ. | last7 = Zichner | first7 = T. | last8 = Lambert | first8 = SR. | last9 = Ryzhova | first9 = M. | title = Recurrent somatic alterations of FGFR1 and NTRK2 in pilocytic astrocytoma. | journal = Nat Genet | volume = 45 | issue = 8 | pages = 927-32 | month = Aug | year = 2013 | doi = 10.1038/ng.2682 | PMID = 23817572 }}</ref>
 
==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<ref>{{Cite journal  | last1 = Metts | first1 = RD. | last2 = Bartynski | first2 = W. | last3 = Welsh | first3 = CT. | last4 = Kinsman | first4 = S. | last5 = Bredlau | first5 = AL. | title = Bevacizumab Therapy for Pilomyxoid Astrocytoma. | journal = J Pediatr Hematol Oncol | volume =  | issue =  | pages =  | month = Mar | year = 2017 | doi = 10.1097/MPH.0000000000000824 | PMID = 28338567 }}</ref>
 
==See also==
*[[Neuropathology tumours]].
*[[Astrocytoma]].
 
==References==
{{Reflist|2}}


[[Category:Diagnosis]]
[[Category:Diagnosis]]
[[Category:Neuropathology tumours]]
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