ESR1 and breast cancer: However, multiple studies have shown that the frequency of estrogen receptor(ER) negative (-) /progesterone receptor(PR) negative (-) breast cancer as well as ER-/PR-/human epidermal group factor receptor 2 (HER2) negative (-) tumors, a subtype of the disease with fewer treatment options and a poorer prognosis than other subtypes, is higher in Latinas compared to NLW [2–7].