ESR1 and breast cancer: These categories consist of breast cancer characterized by the presence of estrogen and progesterone hormone receptors (ER+ or PR+), breast cancer with amplified human epidermal growth factor receptor 2 (HER2+), and triple-negative breast cancer (TNBC), which does not exhibit estrogen receptor (ER-), progesterone receptor (PR-), or human epidermal growth factor receptor 2 (HER2-) expression (50–53).