ESR1 and breast cancer: The prognosis and over all survival of breast cancer has improved over years, with current 10 year relative survival of about 70% in western population.94,95 Positive lymph node status, tumor size, PR and ER, HER-2 are the most reliable prognostic factors in predicting overall as well as disease free survival of breast cancer patients.96 The knowledge of individual prognostic marker remains poorly understood at molecular level in breast cancer prognosis and prediction of particular treatment regimens and its overall survival.