ESR1 and breast carcinoma: In breast carcinoma cases, discordance of ER, PR and HER2/neu status between the primary tumor and subsequent metastases is well recognized.15 Several studies have shown substantial discordance rates between primary breast carcinoma and metastatic disease, reporting hormone receptor discordance rates between 30% and 40%.16,17,18 The primary tumor in our patient was ER-/PR-positive.