Ductal carcinoma in situ and invasive ductal carcinoma differ in depth of tumor invasion, treatment methods and prognosis. 1. Depth of tumor invasion: Ductal carcinoma in situ and invasive ductal carcinoma are mainly differentiated by the depth of tumor invasion. Ductal carcinoma in situ is a kind of early-stage cancer in which the cancer cells are confined to the epithelium but have not broken through the basement membrane, and metastasis usually does not occur. If the depth of tumor invasion exceeds the submucosal layer, then it is invasive ductal carcinoma of the breast, which may have metastasis to the surrounding lymph nodes or distant metastasis. 2. Treatment: Ductal carcinoma in situ is usually treated by radical surgical excision, and generally does not need radiotherapy after surgery. On the other hand, invasive carcinoma should be treated with surgery, radiotherapy and chemotherapy according to the presence or absence of lymph node metastasis and distant metastasis. 3. Prognosis: The prognosis of ductal carcinoma in situ is better than that of invasive ductal carcinoma, and it can be clinically cured. Invasive ductal carcinoma has a small possibility of clinical cure and generally has a relatively poor prognosis. Whether it is ductal carcinoma in situ or invasive ductal carcinoma, after diagnosis, you need to go to hospital for professional treatment and be positive and optimistic.