Gastric neuroendocrine cell hyperplasia and type 1 tumours occurring within gastric hyperplastic polyps.

We wish to highlight the unusual occurrence of gastric neuroendocrine cell hyperplasia and type I neuroendocrine tumours within three hyperplastic polyps. In all cases, the neuroendocrine component was present within and between the hyperplastic foveolar glands of the polyps and overall formed the minor part of the polyps. Two of the patients presented with epigastric pain and the other with fatigue from anaemia, and on endoscopy, all three were found to have superficially ulcerated gastric polyps in the body (cases 1 and 2) and fundus (case 3). Two of the cases had serologically proven autoimmune atrophic gastritis, while the third case had histological evidence of an atrophic gastritis, most likely also autoimmune in aetiology. Cases 1 and 3 had single hyperplastic polyps, while case 2 had three polyps. All polyps showed linear neuroendocrine cell hyperplasia within hyperplastic foveolar epithelium both at the surface and within deeper-situated glands. Neuroendocrine immunohistochemistry highlighted the neuroendocrine cell hyperplasia. The bulk of the neuroendocrine component was restricted to hyperplastic mucosa forming the polyps. Non-hyperplastic adjacent mucosa showed less prominent neuroendocrine cell hyperplasia. It is unclear whether the two pathologies occurred simultaneously or independently. The common feature and causal link is atrophic gastritis, which predisposed the gastric mucosa to the development of both neuroendocrine cell hyperplasia and tumours, and hyperplastic polyps.