The analysis of immunophenotype of gastrin-producing tumors of the pancreas and gastrointestinal tract

BACKGROUND: Gastrinomas are located more frequently in the pancreas, which normally has no cells that can produce gastrin. They have a more aggressive course than other pancreatic endocrine tumors and extrapancreatic gastrinomas associated with multiple endocrine neoplasia Type 1 syndrome. The current study analyzed immunophenotypes of gastrinomas and compared them with other pancreatic endocrine tumors. METHODS: Twenty-one formalin-fixed, paraffin-embedded specimens (15-tumors in the pancreas, 1 in the duodenum, 1 in the stomach, 1 in the liver, and 3 of unknown primary location) accompanied by Zollinger-Ellison syndrome and 17 other pancreatic endocrine tumor specimens were investigated. They were stained immunohistochemically for gastrin, chromogranin A, synaptophysin, insulin, glucagon, somatostatin, pancreatic polypeptide, calcitonin, serotonin, chorionic gonadotropin, adrenocorticotropic hormone, carcinoembryonic antigen, epithelial membrane antigen, and cytokeratin 19. RESULTS: Gastrinomas coexpressed neuroendocrine and exocrine markers, including chromogranin A, synaptophysin, carcinoembryonic antigen, cytokeratin 19, and epithelial membrane antigen. Carcinoembryonic antigen was found in all 17 gastrinomas (100%), cytokeratin 19 was found in 15 of 17 (88.2%) gastrinomas, and epithelial membrane antigen was found in 16 of 18 (88.9 %) gastrinomas. Cytokeratin 19, epithelial membrane antigen, and carcinoembryonic antigen were not found to be present in the pancreatic endocrine tumors, but chromogranin A and synaptophysin were. Chorionic gonadotropin was found in 16 gastrinomas (100%), but only in 2 of 17 other pancreatic endocrine tumors (11.8 %). CONCLUSIONS: Pancreatic gastrinomas were characterized by the coexpression of neuroendocrine markers, exocrine markers, and chorionic gonadotropin. Therefore, pancreatic gastrinomas made a special intermediate group of tumors, which phenotypically combined features of neuroendocrine and exocrine neoplasms. These findings suggested that sporadic pancreatic gastrinomas and other pancreatic endocrine tumors are different phenotypically and are possibly of different origin.