The formation of lung carcinoma in situ is caused by various factors that lead to abnormal proliferation and differentiation of lung epithelial cells, causing atypical hyperplasia and resulting in malignant tumor foci. Lung carcinoma in situ is one of the types of lung cancer. It is caused by malignant lesions of lung epithelial cells due to the action of various carcinogenic factors, but the malignant tumor cells that cause lung carcinoma in situ are limited to the lung epithelium and will not infiltrate and metastasize. Therefore, patients with carcinoma in situ can be cured if the lesion is completely removed through surgery. The prognosis of lung carcinoma in situ is much better than other types of lung cancer after treatment. However, if one does not receive timely treatment, the tumor tissue will infiltrate and the tumor cells will metastasize. Once diagnosed with lung carcinoma in situ, consult doctor in time and surgery should be preferred according to doctor’s advice.