While hormonotherapy and HER2-targeted therapy are considered as treatments of choice for patients with luminal—estrogen receptor (ER)-positive—and HER2-amplified breast cancer subtypes [1], few therapies are available for breast tumors that become resistant to treatment or for triple-negative breast cancer (TNBC), that do not express ER nor HER2 receptors. The gene discussed is ESR1; the disease is triple-negative breast carcinoma.