View source for High-grade astrocytoma with piloid features

'''High-grade astrocytoma with piloid features''' is a rare [[Glioma|glial]] tumor which often requires methylation analyis to secure diagnosis. There is currently no definitive grading, but clinical behaviour suggests WHO CNS grade 3.


=Clinical=
*Rare (1-3% of all brain tumor in adults).
*Usu. posterior fossa (75%).
*Supratentorial or spinal locations possible.
*Imaging may be similiar to [[Glioblastoma]].
*5-year OS: 50%.

=Histology=
*Often so variable, so molecular testing is essential to secure diagnosis.
*Astrocytic nature of tumor cells.
*Frequent mitoses.
*Elongated glial tumor cell processes ("piloid").
*Rosenthal fibers or eosinophilic granular bodies.
*Perivascular lymphocytic cuffing.
*Necrosis may be present.

=IHC=
*[[GFAP]]+ve.
*ATRX: nuclear loss in approx. 40%.


=Molecular=
*DNA Methylation profile of high-grade astrocytoma with piloid features is essential for diagnosis.
*MAPK genes often altered (NF1, BRAF fusion, FGFR1, KRAS).
*CDKN2A/B homozygous deletion.
*CDK4 amplification.
*TERT promotor mutations are rare.
*Absence of IDH1/2 hotspot mutation.


=DDx:=
*[[Glioblastoma]]
*[[Pleomorphic xanthoastrocytoma]]

=See also=
*[[Astrocytoma]].
*[[Neuropathology_tumours#Infiltrative_astrocytomas]]

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[[Category:Diagnosis]]