A novel MLH1 mutation in a Japanese family with Lynch syndrome associated with small bowel cancer.

Lynch syndrome is a genetic disorder related to cancer predisposition, including colorectal cancer, endometrial cancer, and ovarian cancer. Germline mutations in mismatch repair genes, including MLH1 , MSH2 , MSH6 , and PMS2 , are responsible for this condition. Cancer tissue specimens resected from small bowel adenocarcinoma in a Japanese patient showed decreased expression of MLH1 and PMS2 by immunohistochemistry testing. Finally, a novel MLH1 mutation, c.1833dup, was identified in this patient.