ESR1 and invasive ductal breast carcinoma: Patient No. 1, a premenopausal 43-year-old woman, developed right breast cancer (invasive ductal carcinoma, stage T2N0M0, Figure 2) that was estrogen receptor (ER)-negative, progesterone receptor (PR)-negative, and human epidermal growth factor receptor 2 (HER2)-negative (i.e., triple-negative) in January 2016.