Theoretically, ductal carcinoma in situ is a tumor that is confined to the ducts and lobules of the breast and does not metastasize systemically.
If breast-conserving surgery is performed, there is some chance of recurrence, but no metastasis. In the case of breast cancer in situ, especially ductal carcinoma in situ, endocrine therapy can be given after surgery based on the results of postoperative immunohistochemistry, which can significantly reduce the recurrence of breast cancer after surgery for breast cancer in situ, especially if total mastectomy is performed, which can prevent the occurrence of contralateral breast cancer.
The risk of recurrence and the probability of contralateral breast cancer is significantly increased if the tumor is large, and this ipsilateral breast recurrence or contralateral breast cancer can be significantly reduced by endocrine therapy, which is often chosen as the drug of choice.