Carcinoids of the duodenum. A histologic and immunohistochemical study of 65 tumors.

The light-microscopic and immunohistochemical characteristics of 65 duodenal carcinoids are presented. Most tumors showed a mixture of cribriform, insular, glandular, solid, and trabecular growth patterns. Eighty-five percent of the tumors were argyrophil and 15% argentaffin. The nonspecific neuroendocrine markers chromogranin, Leu-7, and neuron-specific enolase were positive in 97, 91, and 83% of tumors, respectively. Immunoreactivity for specific hormones/amines were as follows (percent positive tumors): somatostatin, 47%; N-gastrin, 56%; serotonin, 39%; calcitonin, 19%; insulin, 5%; pancreatic polypeptide, 3%; adrenal corticotropic hormone, 0%; glucagon, 0%. Sixty-eight percent had gastrin/cholecystokinin-like reactivity. Ten psammomatous tumors were located near the ampulla; eight were somatostatin positive, including two in patients with neurofibromatosis. One additional tumor in a patient with neurofibromatosis lacked psammoma bodies but elaborated somatostatin. Eight additional tumors in nonneurofibromatosis patients produced solely somatostatin. Duodenal carcinoids often elaborate more than one polypeptide hormone; those in the ampulla often elaborate somatostatin and have psammoma bodies.