Breast cancer etiology is strongly dependent on reproductive hormones, in particular estrogens (16), both endogenous and exogenous, as exposure to such hormones has been proven to be directly linked to increased risk of breast cancer (17, 18); hormone receptor-positive types of breast cancer are clinically more responsive to hormonal treatment compared to hormone receptor-negative tumors. The gene discussed is NR4A1; the disease is breast carcinoma.