Considering the epidemiological importance of obesity and breast cancer, the aim of this study was to increase knowledge about the relationship between measures commonly used to define obesity (BMI, WC, HC, WHR) and possible changes in breast cancer biomarker expression (ER, PgR and Ki-67) after three weeks of either anastrozole or tamoxifen neoadjuvant treatment in postmenopausal women with breast tumors expressing hormone receptors. The gene discussed is ESR1; the disease is obesity due to melanocortin 4 receptor deficiency.