In early stage, lung cancer is not obvious on X-ray. Only in the middle and late stage, the lung cancer mass increases and is directly shown as mass shadow on X-ray plain film, which is generally divided into peripheral type and central type. Early lung cancer X-ray signs: 1. Central type lung cancer: early stage may have no abnormal manifestations, but it may also manifest as: limited emphysema, obstructive mucus retention sign, inflammatory changes, etc., sometimes accompanied by pulmonary atelectasis and unilateral lung door shadow enlargement. 2.Peripheral type lung cancer: There may be no abnormality in the early stage, or it may be isolated garden or oval shaped block shadow around the lung field, or nodular isolated shadow, pale lamellar shadow, sometimes cavity formation, or reticular or striated shadow is seen. Since X-ray is not sensitive to early lung cancer, CT examination should be performed to detect lesions at an early stage for diagnosis and facilitate timely treatment.