RESUMEN
Primary papillary tumors of the central nervous system are rare. We have encountered a series of six papillary tumors of the pineal region with distinctive features that appear to represent a clinicopathologic entity. The tumors occurred in four women and two men, ranging in age from 19 to 53 years. Imaging studies showed a large well-circumscribed mass in the pineal region. The tumors were characterized by an epithelial-like growth pattern, in which the vessels were covered by a layer of tumoral cells. In papillary areas, the neoplastic cells were large, columnar or cuboidal, with a clear cytoplasm. Nuclei, round or infolded, were found generally at the basal pole of tumoral cells. Immunohistochemically, the tumor cells showed strong staining for cytokeratin, S-100 protein, neuron-specific enolase, and vimentin but only weak or no staining for epithelial membrane antigen and glial fibrillary acid protein. Ultrastructural examination of two cases revealed abundant rough endoplasmic reticulum with distended cisternae filled with secretory product, microvilli, and perinuclear intermediate filaments. The morphofunctional features of these papillary tumors of the pineal region, remarkably uniform within this series, are similar to those described for ependymal cells of the subcommissural organ, and the papillary tumors of the pineal region may be derived from these specialized ependymocytes.