Although there were no significant differences in family history of malignancy, tumor location, pathological T stage, histological type, histological grade, or ER, PR, HER2, p5,3 and Ki67 expression between the case and control groups, the metastatic axillary lymph node ratio, and ratio of tumor size ≥ T2 were significantly lower in the case than in the control groups, suggesting that breast cancer patients who are positive for HBsAg at the time of initial diagnosis are less likely to have axillary lymph node metastasis and more likely to have smaller tumors. This evidence concerns the gene ESR1 and breast cancer.