Somatostatinoma of the duodenum.

An adenocarcinoma of the second portion of the duodenum in a 26-year-old male is presented. The patient was suffering from pain in the epigastrium. Immunofluorescent studies revealed that it consisted almost exclusively of cells with a distincly positive somatostatin-like immunoreactivity. Ultrastructurally, the cytoplasm of the tumor cells had numerous large round granules (about 400 micrometers) with variable electron density. Most of these cells closely resembled the D cells normally seen in the duodenum and the islets of the pancreas, although a few argyrophil cells could be demonstrated by light microscopy. Radioimmunoassay of extracts of the tumor revealed a large amount of somatostatin (2260 pg/mg); substance P and VIP were detected also. Somatostatinoma has been known to occur in the pancreas, but this seems to be the first somatostatinoma found in the intestine.