The CT feature of small cell lung cancer is a soft tissue mass occurring near the hilum with uneven density and irregular shape. Small cell lung cancer is a special type of lung cancer with high malignancy, and patients with CT scan can find that it is mostly central lung cancer, and the direct sign of CT is soft tissue mass with irregular shape and uneven density around the hilum, and the secondary signs caused by the compression or obstruction of bronchial tubes of the mass are obstructive atelectasis, obstructive pneumonia or emphysema, and so on. If small cell lung cancer is peripheral lung cancer, it usually presents as an isolated mass in the lung, and the imaging manifestation of mediastinal lymph node metastasis may appear at an early stage.