Perispheroidal rosettes in irradiated pineocytoma

An ultrastructural study of a pineocytoma was carried out to better define the characteristics of this unusual tumor. Typical light microscopy features of pineocytoma were present: cells arranged in nests and rosettes, a background of fibrillary stroma, and rich vascularity. Characteristic ultrastructural features of pineocytoma were identified: light and dark cells, numerous tumor cell processes, dense core and clear vesicles, microtubules, filaments, and fibrous bodies. However, unlike previously described cases, scattered rosettes were formed around central spheroids with a peripheral corona of small nerve terminals. These perispheroidal rosettes may be analogous to photoreceptor structures or may represent structures formed in response to tumor irradiation.