ESR1 and breast carcinoma: A study of 2821 breast cancer patients in a tertiary hospital in Malaysia reported that 47.5% of patients were ER/PR-positive and HER2-negative, 15% were ER/PR/HER2-positive, and 17.9% were ER/PR-negative and HER2-positive, while 19.6% were ER/PR/HER2-negative [6].