The development process of lung adenocarcinoma is generally the process of lung carcinoma in situ, lung microinfiltrative adenocarcinoma, and invasive adenocarcinoma. Generally, the development from carcinoma in situ to microinvasive adenocarcinoma and invasive adenocarcinoma is a relatively long stage. For example, when a CT screening of the chest is done, a ground glass-like nodule is found, which is consistent with the characteristics of carcinoma in situ, and generally within 5-6 years, the imaging features do not change much. Only after the development of microinvasive adenocarcinoma or infiltrative adenocarcinoma, with a diameter of more than 1 cm, does the development speed up, the cellular component increases, and the volume of multiplication increases. Once the solid nodule reaches more than 1 cm, the development is faster and usually reaches 3 cm in about six months, so it is important to know this rule well to facilitate guidance to patients.