Use

This test is used to identify individuals with hereditary diffuse gastric cancer (HDGC) syndrome by detecting single‑nucleotide variants, deletions, and duplications in the CDH1 gene. It is indicated for individuals with a personal or family history of diffuse gastric cancer or lobular breast cancer, with genetic counseling and informed consent strongly recommended before testing. The person in the family with the earliest or youngest age–related diagnosis should ideally be tested first. Positive (pathogenic or likely pathogenic) results confer a significantly increased lifetime risk of diffuse gastric cancer (up to ~83% for women, ~67% for men) and elevated risk of lobular breast cancer in women (~39–52%), and NCCN guidelines recommend enhanced surveillance, prophylactic surgery, and genetic counseling for family members. Negative and VUS results must be interpreted in the context of personal and family history, and variant interpretation may change over time.