Paraffin sections show a moderately hypercellular tumour which appears to be composed of a mixture of fibrillary astrocytes and cells with features of neurocytes and ganglion cells. Many multinucleated immature ganglion cells are noted throughout the tumour. Tumour cells have a haphazard arrangement. No mitotic figures are identified and there is no evidence of vascular endothelial cell hyperplasia or necrosis. Prominent vessels with hyalinised walls are noted in some areas of the tumour. Tumour cells show moderately strong surface immunostaining for synaptophysin and fibrillary astrocytes show strong staining for GFAP. An occasional ganglion cell shows nuclear NeuN staining. The features are of a low grade glioneuronal tumour favouring ganglioglioma. The topoisomerase labeling index is <1%.
DIAGNOSIS: Low grade glioneuromal tumour with features favouring ganglioglioma (WHO Grade I)