Carcinoma in situ is a kind of early malignant tumor, which has not yet infiltrated into the surrounding tissues. Most patients have a longer survival time after standardized treatment, which can reach more than 5 years or even be cured. However, carcinoma in situ is difficult to be detected in early stage, and patients usually have no special symptoms and are mostly found during physical examination. In situ carcinoma of the lung, for example, can be divided into adenocarcinoma in situ, squamous carcinoma in situ and others according to different pathological nature. Through surgical radical treatment, patients have higher 5-year survival rate or even 10-year survival rate, i.e. more patients have no recurrence for more than 5-10 years, which is called clinical cure, and generally patients can have regular review after surgery for non-in situ cancer.