Cytologic features of the normal pineal gland of adults

Abstract

It is well known that the histology of normal pineal gland may resemble not only pineal tumors but also gliomas, owing to its cellularity which is much greater than that of normal white or gray matter. Our recent experience with a case in which part of a normal gland was submitted for intraoperative consultation, together with the scarcity of cytologic descriptions, led us to perform a cyto-histologic correlation study. In addition to the intraoperative case, we collected five pineal glands from consecutive adult autopsies. During the squash procedure, we often noted the presence of calcified grains. Smears were hypercellular, distributed in tissue fibrillary fragments and as numerous single cells, with crystalline structures. Pineal gland cells (pineocytes) were large, round, epithelioid with ill-defined cytoplasms and moderate nuclear pleomorphism. Spindle cells with greater fibrillary quality were less common. One of the most remarkable findings seen in all cases was the presence of cytoplasmic pigment. Histological evaluation and immunohistochemical staining confirmed that the tissue was normal pineal gland. The histology showed a characteristic lobular aspect and frequent corpora arenacea. The pigment seen cytologically was also encountered in histology and corresponded to lipofuscin. Cytologic features of the pineal gland are peculiar when compared to other normal structures of the central nervous system. These features correlate closely with what is seen on histology. In an adequate clinical context, and in combination with frozen sections, cytology allows a specific recognition of the pineal gland during intraoperative pathologic consultations.