High-density shadow in the lung is not necessarily a tumor. There are several cases as follows: First, those who have had inflammation, tuberculosis, or other lesions in the past, and then may have high-density shadow in the lung during the review of CT, which needs to be reviewed regularly not to be a tumor. Secondly, patients with recent chest pain, chest pain, coughing up blood or wasting, weakness, night sweats, and suspected tuberculosis may also have high density shadow in the lungs. In addition, high-density shadow in the lung can also appear if lung cancer is suspected, but inflammation is usually not a high-density shadow but a light flaky image. To sum up, most of the high-density images in the lungs are left over from inflammation and do not require special treatment, but need to be reviewed. If there are any symptoms in the periphery, such as pleural depressions, or if there are cords, it is necessary to review them periodically, and malignant tumors of the lung cannot be excluded.