CDH1 and Hereditary breast cancer: The 2020 HDGC genetic testing guidelines recommend CDH1 analysis in individuals or families who meet defined clinical criteria, which include either a family history of DGC and/or early onset lobular breast cancer, or individual features (e.g., early onset DGC; DGC in the context of Māori ancestry or cleft lip/palate; combined DGC and lobular breast cancer before age 70; bilateral early onset lobular breast cancer; gastric in situ signet ring cells/pagetoid spread of signet ring cells before age 50).