Familial Gastric Polyposis and Adenocarcinoma (#69)
Surveillance for the intestinal form of gastric adenocarcinoma is feasible and effective, but is only warranted in patients at relatively high risk of this form of gastric cancer. Intestinal gastric cancer is an occasional feature of Lynch syndrome and Li-Fraumeni syndrome.
Hereditary diffuse gastric cancer is due to familial mutations in CDH1 leading to loss of the protein E-cadherin. Carriers of CDH1 mutations are at high risk of diffuse gastric cancer, but there are no macroscopic clues that could be the basis for surveillance. The recommended management is risk-reducing gastrectomy in early adulthood even if the gastric lining appears normal.
Surveillance in patients with gastric polyposis presents the opposite challenge – too many targets rather than too few. Patients with familial adenomatous polyposis, generalised juvenile polyposis, Puetz-Jeghers syndrome, and Cowden syndrome may develop gastric polyposis – but the cancer risk is predominantly in other organs. The commonest cause of gastric polyposis is drug-induced (PPIs), and the risk of gastric cancer is very low.
We describe a new syndrome characterised by fundic gland polyposis and gastric cancer in a large Australian family and smaller North American families. We refer to the syndrome as Gastric Adenocarcinoma and Proximal Polyposis of the Stomach (GAPPS). The disorder exhibits variable expression and incomplete penetrance coupled with a significant risk of gastric cancer that is masked by the polyposis. Analysis of the genes known to cause gastric polyposis was normal.
The key clinical features of this disorder are gastric polyposis with dysplastic fundic gland polyps, exclusive involvement of the gastric body and fundus, an inverse association with H. pylori infection, sparing of the remainder of the gastrointestinal tract, and autosomal dominant mode of inheritance. At-risk family members require regular endoscopic surveillance and, depending on the individual’s physical maturity and degree of polyposis, prophylactic gastrectomy.