There is no obvious correlation between breath malodor and staging of lung cancer patients. At present, the staging of lung cancer is mainly based on three indicators: primary tumor, lymph node metastasis and distant metastasis. 1. Primary tumor: T1 refers to the tumor with a maximum diameter of ≤3cm, surrounded by lung tissues and visceral pleura without invasion of the main bronchus; T2 includes: the tumor with a maximum diameter of 3~5cm, invasion of the main bronchus without invasion of the rondulet, invasion of the visceral pleura, and the presence of obstructive pneumonia or lung atelectasis. T3 includes: the maximum diameter of the tumor is 5~7 cm, invasion of chest wall, phrenic nerve, pericardium, and the appearance of whole lung dysplasia; T4 includes: the maximum diameter of the tumor is >7 cm, invasion of the mediastinum, heart, great blood vessels, tracheal ronchi, main trachea, esophagus, vertebral body, and diaphragm. 2. Lymph node metastasis: N1 includes: ipsilateral intrapulmonary, hilar or peribronchial lymph node metastasis; N2 includes ipsilateral mediastinal or subglottic lymph node metastasis; N3 includes contralateral mediastinal, contralateral hilar, ipsilateral or contralateral obliquus muscle and supraclavicular lymph node metastasis. 3. Distant organ metastasis: M0 indicates that no distant metastasis is detected, and M1 indicates the occurrence of distant organ metastasis. However, there is no correlation between the stage of lung cancer and bad breath odor. It is suggested that patients should go to the hospital as early as possible to get a clear clinical staging in time and get scientific and reasonable treatment under the guidance of professional doctors.