Carcinoma in situ and minimally invasive lung adenocarcinoma are malignant tumors in the lungs, and the main difference lies in the degree of lesion, treatment mode and prognosis. 1. Degree of lesions: carcinoma in situ has not yet broken through the basement membrane and is located in the epithelial layer. Microinvasive lung adenocarcinoma has begun to break through the mucous layer and invade the surrounding tissues. 2. Treatment: carcinoma in situ is usually treated by radical resection through surgery, while microinvasive lung adenocarcinoma needs to be controlled by postoperative radiotherapy in addition to surgical resection. 3. Prognosis: The prognosis of carcinoma in situ is generally very good, and most of them can be clinically cured. Microinvasive lung adenocarcinoma has a higher probability of recurrence and metastasis after surgery than in situ cancer. When malignant tumors are detected in the lungs, it is recommended that patients should seek medical treatment as early as possible and under the guidance of clinicians, in order to prevent delayed treatment.