ESR1 and breast cancer: A comparison between the breast carcinomas of patients diagnosed with and without OPPMs revealed no difference in ER-positivity (84% in patients with OPPMs versus 86% in patients only with breast cancer) but lower expression of PgR in patients with OPPMs (55% in patients with OPPMs versus 71.4% in patients only with breast cancer) and more frequent axillary lymph node metastasis (29.5%) in patients with OPPMs.