Gastric cancer is the third most common malignancy worldwide.1 Outcomes are poor with 5-year survival estimates of 30% and 5% for all stages and for metastatic disease, respectively.2 Environmental factors, such as Helicobacter pylori infection, diet, and tobacco use, are strong risk factors that likely underlie many gastric cancer cases.3 In 5% to 10% of cases, there is familial clustering of gastric cancers, and, although shared environmental risk factors could explain some of this clustering, hereditary syndromes owing to genetic mutations are known to increase gastric cancer risk.