ESR1 and breast cancer: Lymph node metastasis (39.8% versus 38.0%, p < 0.001) and ER positivity (60.7% versus 57.1%, p < 0.001) were more frequent in premenopausal breast cancer patients, while Her-2/neu positivity was more common in postmenopausal than in premenopausal breast cancer patients (24.5% versus 23.2%, p = 0.026).