||Familial diffuse gastric and lobular breast cancer predisposition, diagnostic test. The CDH1 gene encodes the cell adhesion protein e-cadherin. E-cadherin germline mutations are associated with both hereditary diffuse gastric cancer and lobular breast cancer. The inheritance pattern is autosomal dominant with incomplete penetrance (~80% for diffuse gastric cancer and ~40% for lobular breast cancer). Mutations are widely distributed throughout the gene, and associated with loss of function of the mutated e-cadherin allele. By the time gastric cancer becomes symptomatic, it is rarely curable. However, a high cure rate (>90% 5 year survival) is possible if the stomach is removed prior to tumor invasion through the gastric wall. Identification of individuals at high risk of developing diffuse gastric cancer, then, affords the opportunity for elective prophylactic gastrectomy. The e-cadherin gene locus (CDH1) is tested for the presence of sequence variants by polymerase chain reaction followed by direct DNA sequencing of the 16 exons as well as surrounding non-coding regions. Because mutations are distributed across all coding exons of the CDH1 gene, an analysis of all exons is recommended. For families with a known mutation, sequencing of a single exon may be appropriate. This is offered separately in our laboratory. For more about Familial Gastric Cancer click here.