Lung cancer cavity usually disappears abnormally. Lung cancer belongs to common malignant tumors in respiratory system. The formation of lung cancer cavity is mainly due to too fast growth of lung malignant tumors and insufficient blood supply, which results in necrosis of tumor tissues, and the tissues are gradually liquefied after necrosis and discharged out of the body through trachea, bronchial tube, and mouth, making the lungs form cavities. This kind of lung cancer cavity usually does not disappear and will invade the surrounding tissues if treatment is not complete. It is worth noting that for cavities <2cm in diameter, the diagnosis of lung cancer should be cautious, which may be caused by cryptococcal infection or bronchiectasis with infection. Tuberculosis can also cause lung cavities. Therefore, the cause of the cavity should be determined first. If the above symptoms appear, it is recommended to "early detection, early diagnosis, early treatment" to minimize the adverse effects of the disease, and early formal treatment.