Benign Tumours of the stomach are uncommon. Polyploid adenomas occur in less than 1 % of the population and may occur in association with intestinal metaplasia. They predispose to carcinoma. Gastric polyps occur in familial adenomatous polyposis (in up to two-thirds of patients, but with a lower potential for malignant transformation than the colonic adenomas, in MUTYH-associated polyposis, in Peutz–Jeghers syndrome, and in Cowden syndrome.
Gastric polyposis (with malignant potential) limited to the stomach has been described in three generations of a family (dos Santos and de Magalhes 1980). Recently three families with an autosomal dominantly inherited syndrome characterized by fundic gland polyposis and intestinal-type gastric cancer was described (gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS)) (Worthley et al. 2012). Recommended diagnostic criteria for GAPPS were (1) gastric polyps restricted to the body and fundus without colorectal or duodenal polyposis, (2) >100 polyps carpeting the proximal stomach in the index case or >30 polyps in a first-degree relative of another case, (3) predominantly fundic gland polyps with regions of dysplasia or gastric adenocarcinoma, and (4) autosomal dominant inheritance. Earliest age at diagnosis of gastric cancer was 33 years of age. Relatives at high risk should be offered surveillance gastroscopy, and partial gastrectomy should be considered in affected cases.
Hyperplastic gastric polyps are five times as common as gastric polyps and have a much lower risk of malignancy. They are found with increased frequency in pernicious anemia and in familial adenomatous polyposis (Debinski et al. 1995) and the Peutz–Jeghers syndrome (Ushio et al. 1976; Williams et al. 1982). Carcinoids, lymphomas, sarcomas, and leiomyosarcomas may also arise in the stomach; a family with primary B cell gastric lymphoma in a father and his two daughters has been described (Hayoz et al. 1993).