When you get a chest X-ray or CT report, you see “a nodular shadow in the lung is found, tumor cannot be excluded, follow-up is recommended”. In this age of cancer fear, there is no one who is not afraid of it. What is a nodule? Nodules are other tissues that are not part of the normal alveolar structure and may be scars, inflammation, benign tumors or malignant tumors. Because nodules are denser than normal inflated alveoli, they appear as shadows on x-ray. Doctors classify the shadows according to their size, shape and density: lamellar shadows, reticular shadows, spherical shadows, mass shadows and nodular shadows. Nodular shadows are round shadows of relatively small to medium density. The less dense ones appear as translucent nodular shadows on CT, which are also called ground glass shadows. What should I do if I encounter this situation? The answer is to see a respiratory, radiology or thoracic specialist and get their opinion. If other tumor indicators test negative, the common treatment methods by doctors are as follows: 1. Follow up. It is to review the CT every 3, 6 or 9 months to see the change of the shadow. If the shadow becomes smaller or never grows, it indicates that the nodule is benign. On the contrary, it is malignant. 2.PET-CT examination. It is helpful to determine the benign and malignant. But not 100%. It is at your own expense, $7,000 to $8,000. 3.Fiber bronchoscopy. 4.Surgical exploration. That is, open surgery.