ESR1 and ductal breast carcinoma in situ: IDC is the predominant type of BC, approximately estimated eighty percentages of all BC cases [29].IDC cancer cells penetrate through the walls of the milk ducts and infiltrate the adjacent breast tissue [30].IDC frequently occurs alongside DCIS and this combination (IDC + DCIS) correlates with improved overall survival compared to IDC alone.The occurrence of DCIS in patients with IDC correlates with advantageous clinical attributes, including reduced T/N stage,low/intermediate grade and progesterone receptor (PR)/estrogen receptor (ER) positivity.