According to the 2020 guidelines, the clinical definition is no longer used, and the definition criteria of HDGC has been replaced by a pathogenic germline variant found in CDH1 or CTNNA1 in an isolated individual with DGC or with a family history of DGC in first-degree or second-degree relatives. The gene discussed is CTNNA1; the disease is CDH1-related diffuse gastric and lobular breast cancer syndrome.