Multicentric gastric carcinoids complicating pernicious anemia. Origin from the metaplastic endocrine cell population.

We report three cases of multicentric carcinoid tumors of the stomach in patients with long-standing pernicious anemia and severe atrophic gastritis (type A). The tumor nodules arose in nonantral gastric mucosa showing marked intestinal metaplasia. Diffuse endocrine cell hyperplasia was present in both fundus and antrum. Antral G-cell hyperplasia was observed. A widely accepted pathogenesis of this syndrome suggests that the proliferating cell type is the argyrophilic, enterochromaffinlike cell native to the gastric body and fundus. Our findings conflict with this view, in that focal argentaffin staining was also present within tumor cells, as well as immunoreactivity for serotonin and substance P (more characteristic of small-intestinal enterochromaffin or Kulchitsky's cells and small-intestinal carcinoids). Findings in these cases at least suggest an alternative possibility: the tumors may derive from small-intestinal-type metaplastic endocrine cells within the atrophic mucosa, rather than the hypertrophic native endocrine cell population.