Duodenal somatostatinoma with psammoma bodies

A duodenal somatostatinoma was found incidentally in a 60-year-old woman undergoing cholecystectomy. Microscopically, the tumor had a glandular architecture with abundant psammoma bodies. Electron microscopy revealed tumor cells resembling D-cells of the pancreatic islets. Immunohistochemically, there was staining for neuron-specific enolase, chromogranin, and diffuse cytoplasmic positivity for somatostatin only. By immunoelectron microscopy, somatostatin was identified predominantly in lucent membrane-bound secretory granules. X-ray-dispersive microanalysis showed the psammoma bodies contained calcium apatite crystals. This case is compared with other reported cases with a description of cellular localization of somatostatin and development of psammomatous calcification.