Paraffin sections show fragments of a densely hypercelullar tumour. This consists of diffuse sheets of cells with uniform round and oval nuclei with an open chromatin arrangement, conspicuous nucleoli and delicate neuropil-like processes. These show nuclear immunostaining for NeuN (not shown), cytoplasmic staining for beta-tubulin (not shown) and membrane staining for synaptophysin. No staining for GFAP is seen. Occasional mitotic figures are identified (2/20HPF). No necrosis is seen. The features are of central neurocytoma. The topoisomerase labelling index is approximately 5%
DIAGNOSIS: Central neurocytoma (WHO Grade II).