The Collaborative Group on Hormonal Factors in Breast Cancer recently published a meta-analysis [1] revealing that: (i) half of the women with breast cancer have used MHT, (ii) an excess risk of breast cancer was associated with 1–4 years of use and progressively increased with MHT duration, (iii) the excess risk was greater for estrogen receptor (ER)-positive (ER+) than ER-negative (ER-) breast cancer, (iv) the risk was higher for estrogen-progestogen than for estrogen-only preparations. The gene discussed is ESR1; the disease is breast cancer.