Gastrinoma of duodenal G-cell origin.

A 65-year-old man with hypergastrinemia associated with the Zollinger-Ellison syndrome was found to have a duodenal "carcinoid-islet cell tumor." Gastrin levels have remained normal for more than 1 year following total gastrectomy and removal of the duodenal tumor. Immunohistochemical studies for gastrin localization revealed positive staining of the tumor and of a population of nonneoplastic G-cells in the adjacent duodenal mucosa and Brunner's glands. These results support the hypothesis that gastrinomas may arise as primary tumors from duodenal G-cells rather than from ectopic pancreatic tissue. "Carcinoidislet cell tumors," like other tumors of APUD-cell origin, may express dual biochemical functions in the form of polypeptide hormone and/or amine secretion. Their content of specific hormonal products may be predicted on the basis of sensitive histochemical and immunohistochemical techniques.