In recent years, the incidence and mortality rate of lung cancer has increased dramatically, and CT examination plays an important role in the diagnosis of lung cancer. The following are some common CT imaging signs of lung cancer in clinical practice. 1.Lobular sign More obvious concave and convex multiple curvilinear manifestations of tumor edge, with the curvature of lobular part as the standard: chord distance/chord length >2/5 is deep lobulation. It is related to the different degree of differentiation of tumor cells and different growth rate of each site. In the bronchus, blood vessels entering and exiting the tumor and pleura trapped parts can form obvious depression and lobulation, CT examination: the incidence is 80%. 2.Spinous protrusion A thick and blunt “pestle-like” structure between lobulation and burr, with infiltration of lung cancer cells. 3.Burr sign A spine-like or burr-like protrusion at the edge of the mass to varying degrees, only seen at the interface between the mass and the lung parenchyma. Generally speaking, the burrs of peripheral type lung cancer are short burrs, while the long and sparse burrs of tuberculoma and chronic inflammation are called long burrs. 4.Pleural depression sign Linear or triangular image between the tumor and pleura, the incidence is about 50%, which is more common in adenocarcinoma and fine bronchoalveolar carcinoma. Formation conditions: contraction of fibrosis in the direction of the tumor, no thickening adhesion of the pleura, fibrosis within the tumor – the underlying dynamics. Influencing factors: the distance between the tumor and the wall pleura. 5.Vacuolar sign Small focal translucent areas within nodules, less than 5MM in diameter, mostly seen in adenocarcinoma and fine bronchoalveolar carcinoma, CT examination: the incidence is 24-48%. The pathological basis of the vacuolation sign: lung tissue not occupied by tumor tissue, unclosed fine bronchi, air-containing cavity between papillary carcinoma structures, unclosed or melted, destroyed or enlarged alveolar cavity. 6.Fine bronchial inflatable sign Fine strips with air density shadow of about 1mm in diameter, the incidence is about 33.3%. Pathological basis: dilated fine bronchioles. 7.Calcification CT examination: the incidence is 6-7%, patchy calcification is located in the center of the tumor, which occurs after tumor necrosis; nodular calcification is mostly located in the periphery, which is caused by the tumor wrapping the original calcification.