ESR1 and ductal breast carcinoma in situ: The principle aim of this study is to provide a comprehensive evaluation of MIBC and associated DCIS in relation to salient clinical and pathological variables including ER, PR, and HER-2 status, number of foci of MIBC, the size extent of the background DCIS and nuclear grade, presence of comedo-necrosis, as well as surgical procedures, adjuvant treatment and clinical follow-up to identify variables which predict disease free survival and influence clinical decision making.