Lung cancer can be classified into small cell lung cancer and non-small cell lung cancer according to histopathologic classification, and non-small cell lung cancer includes squamous carcinoma, adenocarcinoma, large cell carcinoma and so on. 1. Small cell lung cancer: it is a kind of low differentiated neuroendocrine tumor. It has endocrine and chemoreceptor functions and can secrete catecholamines and other substances, causing carcinoid syndrome. Small cell lung cancer generally proliferates faster, metastasizes widely in the early stage, and is more sensitive to chemotherapy and radiotherapy. 2. Non-small cell lung cancer (1) Squamous carcinoma: mostly originated from bronchial mucosa. Generally, it grows slowly, metastasizes later and has more chances of surgical resection. (2) Adenocarcinoma: it is a common type of lung cancer, mainly originated from bronchial mucous glands. Adenocarcinoma is rich in blood vessels, and local infiltration and hematogenous metastasis can occur earlier. (3) Large cell carcinoma: it is undifferentiated non-small cell carcinoma. It develops metastasis at a later stage and has a higher chance of surgical resection. If there is any discomfort, it is recommended to consult a doctor in time.