The sections show a moderately cellular tumour. It often forms rosettes and nests, surrounded by vascularised stroma. The tumour cells have generally round nuclei, granular chromatin, small nucleoli and moderate amounts of eosinophilic cytoplasm. No nuclear moulding is seen. Occasional cells show degenerate nuclear changes with moderate nuclear enlargement and smudged chromatin pattern. No mitoses are seen. There is no endothelial cell hyperplasia or necrosis. The tumour cells are diffusely positive for synaptophysin and neurofilament. The Ki-67 index is 2-3%.
FINAL DIAGNOSIS: pineocytoma (WHO Grade I).