In the process of physical examination, some patients often unintentionally find the presence of lung shadows, are all lung shadows malignant? How to differentially diagnose benign and malignant? Generally speaking, lamellar shadows are more common in benign lesions, such as bacterial infections, accompanied by fever, cough and sputum, especially yellow mucous sputum, which are more indicative of the presence of lung inflammation. Another part of the shadows are spherical or with divided spurs, irregular margins, or the presence of cavities. This part of the cases requires differential diagnostic tests, mainly for tuberculosis globules, misshapen tumors, lung cancer, and capillary sclerosis. Some patients may still be unable to make a clear diagnosis after extensive tests. At this time, an experimental treatment approach can be adopted, mainly by giving anti-inflammatory drugs or anti-tuberculosis drugs based on experience and reviewing chest X-rays or CT films after a period of treatment to understand changes in the condition. The newly developed non-invasive diagnostic method than PET-CT can initially identify benign and malignant by the uptake of glucose by tissue cells, and the accuracy and specificity are relatively high. However, the only way to get an accurate diagnosis is to perform surgical exploration and remove the tissue for pathological examination, which is the “gold standard” of diagnosis.