To determine whether the FEN1 polymorphisms had an effect on the different clinical features of BC patients, we then analyzed the associations between the FEN1 polymorphisms and a series of clinic pathological parameters, including tumor size, lymph node metastasis, the status of the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (Her-2). The gene discussed is ESR1; the disease is breast cancer.