ESR1 and breast carcinoma: <h4>Objective</h4>To investigate the expression characteristics of Ki-67, estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER-2) in breast cancer (BC) patients and to evaluate their associations with lymph node metastasis and clinical disease stage.<h4>Methodology</h4>The clinicopathological data of 122 patients with BC admitted to Affiliated Nantong Hospital 3<sup>rd</sup> of Nantong University from April 2020 to November 2023 were analyzed retrospectively.