Hereditary diffuse gastric cancer (HDGC) is an autosomal dominantly inherited syndrome attributed to mutations of the E-cadherin gene, CDH1. There is no proven effective screening for early HDGC, and symptomatic disease is almost universally fatal. The only available effective option for CDH1 carriers is prophylactic total gastrectomy, but the variable age of onset of HDGC and the reduced penetrance (about 70%) of the CDHI gene further complicate patients' decision making.