Histology was obtained following craniotomy and macroscopic resection.
Paraffin sections show a densely hypercellular astrocytic glioma composed predominantly of gemistocytic cells with a quantitatively smaller component of fibrillary astrocytes. Tumour cells show moderate nuclear and cellular pleomorphism. An occasional mitotic figure is identified. No vascular endothelial cell hyperplasia is seen, and there is no necrosis. The tumour extends through the full thickness of the cerebral cortex. Prominent perivascular cuffing by small lymphoid cells is noted throughout the tumour.
Immunohistochemistry shows moderate staining in tumour cells for IDH-1. The topoisomerase labelling index is approximately 2% (not shown).
Final diagnosis:
Right frontal brain tumour: Gemistocytic astrocytoma (WHO grade II)