Somatostatinoma of Vater's papilla and of the minor papilla.

Two cases of somatostatinomas of the major and minor papilla are reported. The tumors were characterized by solid trabecular and tubular arrangements of tumor cells and in one case by the presence of microvilli and psammoma bodies. The tumor cells contain many amine precursor uptake and dicarboxylation (APUD)-granules with a diameter of 300 to 500 nm and low electron density. Immunoperoxidase stain showed intense staining only for somatostatin and low density of neuron-specific enolase. Those tumors either resulted from pluripotent endocrine cells or from D-cells of the mucosa or glands of the papilla.