MICROSCOPIC DESCRIPTION: The sections show features of a moderately cellular astrocytic tumour. The tumour cells are of mixed fibrillary and protoplasmic types. Small numbers of gemistocytes are also seen. The tumour cells have enlarged hyperchromatic nuclei and variable amounts of cytoplasm. Focal microcystic change is seen in the background. Mitoses are inconspicuous. No endothelial cell hyperplasia or necrosis is present. Tumour cells are seen in the cortex. There is no oligodendroglial component. The features are those of diffuse astrocytoma. The Ki-67 index is 3-4%. IDH-1 immunostain is negative.
FINAL DIAGNOSIS: Diffuse astrocytoma (WHO Grade II).