1-3. The sections show a cellular lesion composed of cells of uniform size with benign nuclear features. The cells form large irregular-shaped rosettes with neuropil at the centre (pineocytoma/neurocytoma-type rosette). There are no multi-nucleated giant cells and no hyperchromatic nuclei. No mitotic activity is identified.
The cytoplasm has positive immunostaining with synaptophysin and neuron-specific enolase (NSE). The tumour cells are negative for GFAP and chromogranin A. The Ki-67 stains approximately 5% of cells.
1-3. PINEAL GLAND:
- PINEOCYTOMA (WHO GRADE I).