The patient went on to have a craniotomy and excision of the mass.
Histology
MICROSCOPIC DESCRIPTION: Paraffin sections show fragments of a densely hypercellular tumour. Tumour cells have small round, oval and angulated hyperchromatic nuclei and delicate processes which show strong immunostaining for neurofilament protein (NFP). Tumour cells are arranged in diffuse sheets. Prominent Homer-Wright rosettes are noted in several areas. Scattered mitotic figures are identified. No areas of necrosis are seen. Tumour cells show strong granular perinuclear immunostaining for synaptophysin. No staining for GFAP or NeuN is seen. The features are of pineoblastoma. The Ki-67/MIB-1 labelling index is approximately 6%.
FINAL DIAGNOSIS: Pineoblastoma (WHO Grade IV)