Pathology
H&E
H&E
H&E
Sections show a variably cellular tumour with a fibrillary background. Tumour cells have elongated bipolar to round nuclei with inconspicuous nucleoli. Frequent Rosenthal fibres are seen. There are focal aggregates of thin-walled, hyalinised blood vessels with the adjacent parenchyma containing hemosiderin deposition consistent with a cyst wall. No mitoses, necrosis or microvascular proliferation are identified.
IMMUNOHISTOCHEMISTRY:
- GFAP: Positive
- Nestin: Positive
- NogoA: Negative
- IDH1 R132H: Negative (non-mutated)
- ATRX: Intact (non-mutated)
- p53: Equivocal
- p16: Negative
- BRAFV600E: Negative
- H3K27M: Negative
- H3K27me3: Intact
- Topoisomerase proliferation index: 1%
FINAL DIAGNOSIS: Pilocytic astrocytoma (WHO grade I).