Breast cancer is not necessarily carcinoma in situ. Generally speaking, in terms of the prognosis of breast cancer, if breast cancer is confirmed to be carcinoma in situ, it is usually recorded as stage 0 clinically and can be cured without chemotherapy or even local excision after surgery. At present, the clinical staging of breast cancer is mainly based on the size of the tumor, whether it is combined with lymph node metastasis and whether it has distant metastasis, and it is classified into stage I-IV. Stage I is the early stage, after timely radical surgical resection, together with postoperative comprehensive treatment, the five-year survival rate can reach more than 80% or even higher. stage 0 is even earlier than stage I, so after timely surgical treatment for stage 0, i.e. carcinoma in situ, most of the patients can be cured without chemotherapy. Stage 0 is earlier than stage Ⅰ, so most patients can be cured without chemotherapy after timely surgical treatment. Breast cancer not only includes stage 0, but also includes stages Ⅰ-Ⅳ, the higher the stage, the lower the five-year survival rate or clinical cure rate, so breast cancer is not necessarily in situ cancer, in fact, the majority of clinical breast cancer is early, progressive breast cancer.