There is no such thing as a complete cure in clinical practice, but there is a clinical cure, which means that the cancer has not recurred for more than five years. After radical treatment of carcinoma in situ, it usually will not recur again, but there is a possibility that the radical treatment is not enough for recurrence. Carcinoma in situ is the earliest stage of cancer, in which the cancer cells are only confined to the epithelial layer, without destroying the basement membrane to invade the dermis or mesenchymal tissues underneath, and without infiltration or distant metastasis of epithelial malignant tumors. Carcinoma in situ mainly occurs in breast, cervix, rectum and so on. Clinical symptoms of carcinoma in situ are not obvious, and most of the patients discover it through physical examination. The treatment of carcinoma in situ is very effective, usually through endoscopic treatment and surgical resection. Carcinoma in situ upholds the principle of early detection and early treatment. After surgery, patients should follow the doctor’s instructions for regular review and closely monitor the surgical site.