The prognosis and treatment of patients with breast carcinoma of no special type (NST) are dependent on a few established parameters, such as tumor size, histological grade, lymph node stage, expression of estrogen receptor (ER), progesterone receptor (PR), overexpression of human epidermal growth factor receptor 2 HER-2), and proliferation index determined by Ki-67 [1-5]. The gene discussed is ESR1; the disease is breast carcinoma.