Novel crystalloid structures in suprasellar paraganglioma.

A-52-year-old woman was admitted to a hospital because of 2-year history of abnormal behavior and impaired visual acuity. Magnetic resonance imaging delineated a sizable mass at the suprasellar region. The partially removed tumor was arranged in irregular lobules composed of an admixture of clusters of cobblestone-like small cells and process-bearing cells with ovoid nuclei, surrounded by a fine, neuropil-like matrix. The Zellballen structure was inconspicuous, and mitosis was absent. Immunohistochemically, the tumor cells were positive for chromogranin A, synaptophysin, class III β-tubulin and neurofilament, while negative for glial fibrillary acidic protein, cytokeratin and all 6 pituitary hormones. S100 protein expression was limited to cells adjacent to stroma. The MIB-1 labeling index was 0.5%. Histopathological diagnosis was paraganglioma of abortive architecture. Ultrastructurally, numerous dense-cored vesicles were found within the processes and cytoplasm. Synapse formation was not demonstrated. Interestingly, crystalloids up to 3 μm in size were frequently found. They had hexagonal or quadrilateral architecture without limiting membranes. The interval between periodically arranged fibrils was variable, ranging from approximately 20 - 50 nm. Retrospective examination by light microscopy failed to reveal corresponding structures. Crystalloids are rare manifestation of paragangliomas, yet undescribed in those of intracranial origin. Furthermore, the ultrastructure of the present case differs from those of previous cases.