Ultrastructure of metastatic rete testis adenocarcinoma

Adenocarcinoma of the rete testis is a rare tumor. We describe the ultrastructural appearance of a retroperitoneal adenocarcinoma metastatic from the rete testis, and compare this appearance with that of normal human rete testis. Both normal rete epithelium and the tumor showed deep, narrow nuclear invaginations with apparent nuclear lobulation; small, pleomorphic, electron-dense, membrane-bound granules in the basal cytoplasm; lipid droplets in the apical cytoplasm; and distinctive bulbous cytoplasmic projections along the apical surfaces of the cells. In addition, more general features of glandular tissue were seen. Features notable for their absence were mucin granules, microvilli containing filamentous cores, glycocalyx, and glycocalyceal bodies. The ultrastructural appearance was sufficiently distinctive to suggest that, in the proper clinical context, electron microscopy may serve to support a diagnosis of adenocarcinoma of the rete testis.