Lung cancer can be initially suspected in high-risk groups with a history of long-term smoking, occupational carcinogens, exposure to ionising radiation and a family history of tumours, with typical symptoms and signs such as irritating choking cough, blood in sputum or haemoptysis, wheezing, chest tightness and unexplained wasting. The diagnosis can then be confirmed by finding cancer cells through pathological examinations such as chest imaging, sputum exfoliation cytology and pleural effusion cytology.