The forty patients, aged 20–67 years, were divided into two groups: the BC group, consisting of 20 women with estrogen-receptor-positive invasive BC [including 18 invasive ductal carcinoma (IDC) and 2 invasive lobular carcinoma (ILC)] and the BBD group comprising women diagnosed with histologically-proven benign breast lesions. Here, ESR1 is linked to invasive lobular breast carcinoma.