To exclude lung cancer, the shadow of lungs should mainly start from the following aspects: 1. Symptoms accompanying the shadow of lungs, if it is accompanied by coughing, coughing up sputum, blood in sputum and fever, first consider the possibility of lung infection. Infectious lesions will be dissipated and absorbed rapidly after anti-infection treatment, usually 1-2 weeks of re-examination of lung CT can see the shadow of the lungs will be dissipated and absorbed, if dissipation and absorption are obvious, then the infectious lesions of the lungs will be considered. 2. The shadow of the lungs can be tuberculosis, which is treated with anti-tuberculosis treatment and has a special effect, and the tuberculosis of the lungs mainly occurs in the dorsal part of the upper lungs and lower lobes of the lungs accompanied with pleural effusions, and bacillus antituberculosis can be found in pleural effusions. In the pleural fluid, antacid bacilli can be found, which can be obviously absorbed after anti-tuberculosis treatment, and also the lung shadow is caused by tuberculosis infection. However, it is important to exclude lung cancer, which is mainly manifested as soft tissue mass with irregular edges and short burrs, accompanied by depression or folding, etc. It can be diagnosed by puncture biopsy of the soft tissue mass to find cancer cells.