Diagnosis and Management of Hereditary Gastric Cancer. 
A positive family history is consistently reported as a risk factor for gastric cancer (GC), but the molecular basis for the familial aggregation is largely unknown.  The risk associated with having one first-degree relative (FDR) with GC is approximately 1.3-3.5 fold increased.  Hereditary cancer syndromes have been relatively well characterised, but their rarity largely precludes the development of trials of surveillance.  In hereditary diffuse gastric cancer (HDGC), patients have a CDH1 mutation that results in a high penetrance of GC meaning that prophylactic gastrectomy is recommended, although this treatment results in significant psychosocial issues.  The management of HDGC patients includes endoscopic surveillance, surgery and histological interpretation which require a high degree of selective expertise.  Much of the remaining heritable risk of GC may be accounted for by low- and intermediate-penetrant genetic factors, i.e. common and rare variants, respectively.  The advent of new methods such as next-generation sequencing has revealed a number of new candidate gene loci.