Paraffin sections show a glial tumour of varying tumour cell density. Tumour cells are a mixture of piloid cells arranged in loose fasciculi and small protoplasmic and fibrillary astrocytes arranged in diffuse sheets. Scattered Rosenthal fibres and granular eosinophilic bodies are noted and areas with a myxomatous/mucinous stroma are also seen. There is prominent microvascular proliferation with endothelial cell hyperplasia. Scattered foci of bland infarct-like necrosis are also seen. No mitotic figures are identified.
IMMUNOHISTOCHEMISTRY:
- GFAP: positive
- IDH-1: negative
- nestin: positive
- p53: negative
- MGMT: negative
Epithelial membrane antigen (EMA) negative
Topoisomerase labelling index is approximately 5%
FINAL DIAGNOSIS: Pilocytic astrocytoma (WHO Grade I)