Non-invasive breast cancer, also known as in situ breast cancer, is a type of breast cancer that is confined to the primary site and has not broken through the basement membrane of the breast ducts and has not metastasized. It can be divided into lobular carcinoma in situ, intraductal carcinoma in situ and eczematous carcinoma of the breast. With early detection and active treatment, the prognosis is generally better. Lobular carcinoma in situ and intraductal carcinoma in situ can appear as breast lumps in early stage, mostly unilateral, hard and not easy to push, most of them are painless; eczema-like carcinoma of breast can appear as itching of unilateral nipple, areola and surrounding skin, with red patchy eczema-like appearance, or ulcers can be formed in severe cases. Non-invasive breast cancer is mainly treated by surgery, and the next adjuvant treatment is decided based on the surgical approach and immunohistochemistry results. If patients have breast-conserving surgery, they need to undergo radiotherapy in time after surgery to reduce the recurrence rate after surgery; if patients have high expression of estrogen receptor or progesterone receptor, they need to do endocrine therapy and can be treated with anti-estrogen drugs, the five-year survival rate of patients after active treatment is up to 90% or more, and the prognosis is generally better.