Subgroup analysis according to ER status showed that an excess risk of breast cancer was restricted to the ER+ cases, with an OR of 3.97 (95%CI: 1.46–10.79) for those with a mother impacted by breast cancer and 2.06 (95%CI: 1.07–3.97) for those who had an impacted sister. The gene discussed is ESR1; the disease is breast carcinoma.