Certain germline genetic syndromes are associated with inherited susceptibility, including hereditary diffuse gastric cancer syndrome (CDH1—cancer risk 70%), Peutz–Jeghers syndrome (STK11—cancer risk 29%), juvenile polyposis syndrome (SMAD4—cancer risk 21%), Lynch syndrome (MLH1, MSH2, (EPCAM deletions), MSH6, and PMS2—cancer risk 1–13%), Li–Fraumeni syndrome (TP53—cancer risk 1–4%), familial adenomatous polyposis (APC—cancer risk < 1%), and a variant of FAP gastric adenocarcinoma and proximal polyposis of the stomach (APC promoter 1B—cancer risk significantly elevated) [26]. This evidence concerns the gene SMAD4 and cancer.