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=See also=
*[[Breast]].
*[[Invasive breast cancer]].
=References=
{{reflist|2}}
[[Category:Breast pathology]]
6e5117b91c9f278fff1fc3c4167d313a6dc1d25aa15311621ed7131ae2ba6a48 librepath-non-invasive-breast-carcinoma.txt
{{ 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>