Germline mutation of the LKB1/STK11 gene with loss of the normal allele in an aggressive breast cancer of Peutz-Jeghers syndrome.

Peutz-Jeghers syndrome (PJS) is an autosomal-dominant polyposis disorder with an increased risk of multiple cancer. The LKB1/STK11 gene, which acts as a tumor suppressor, is responsible for PJS and plays a role in suppressing breast cancer. The low expression of LKB1/STK11 in sporadic breast cancer is significantly associated with shorter survival. Here we describe a PJS patient with aggressive breast cancer that carried not only a germline mutation of LKB1/STK11 but also loss of the normal allele. The combination of these mutations may be associated with the poor prognosis of this patient. To our knowledge, we are the first to show that a germline mutation causing PJS is combined with the loss of the homologous normal allele of LKB1/STK11 in breast cancer.