ESR1 and breast cancer: US cancer incidence data during 2008 and 2012 show that Black women have the lowest incidence of breast cancers characterized as hormone receptor-positive (positive for estrogen receptor [ER] and/or progesterone receptor [PR]) and human epidermal growth factor receptor 2 (HER2)-negative and the highest incidence of hormone receptor-negative and HER2-negative breast cancers when compared to other racial/ethnic groups [1].