Abstract: Lynch syndrome (LS) is an autosomal dominant hereditary disease caused by deletion of such DNA mismatch repair (MMR) genes as MLH1, MSH2, MSH6, and PMS2. The functional loss of MMR genes results in instability of the highly repetitive DNA sequence, and may eventually leads to tumor occurrence. Here we report a case of LS- related endometrial cancer in a clustered LS family identified by genetic counseling and genetic testing. For patients with a family history of LS-related tumors, the diagnosis of LS should be considered, and immunohistochemical testing of MMR and genetic testing for LS should be performed. A definite diagnosis of LS has important clinical significance for individuals and family members, and risk screening and preventive measures can minimize the overall risk of developing LS-related cancers.

Key words: lynch syndrome; endometrial cancer; hereditary disease