Pulmonary carcinoma in situ refers to tumor growth confined to the mucosal layer without infiltration and metastasis, which is an early stage lung cancer and most of them have good prognosis. Most patients with lung cancer in situ do not have any symptoms in the early stage and are usually detected during physical examination. If it is non-small cell lung cancer, the patient can be cured clinically after surgical resection and the survival period can be unaffected. If it is small cell lung cancer, metastasis can occur at an early stage, and adjuvant radiotherapy and chemotherapy should be given after early surgical resection, but the patient’s survival period may not exceed 5 years. However, if the patient is not treated in time, it can gradually develop into invasive cancer and then cause metastasis and spread of cancer cells, which can be life-threatening, and its survival period may be shorter. Therefore, early detection, diagnosis and treatment are crucial to prolong the survival time and improve the quality of life of lung cancer patients, so it is recommended that people over 40 years old should have relevant medical checkups every year.