People often ask: Dr. Zhang, the CT report says I have a nodule on top of my lung, is it lung cancer and what should I do? Here is an explanation for you. Like anything in nature, nodules on the lung grow gradually from small to large and do not become giant at the beginning. Nodules on the lung, in the early stage, are often something called frosted glass nodules, which appear as cloudy faint shadow/circular nodules with mildly increased density on chest CT, looking like frosted glass, so it is also called frosted glass shadow. It can be a diffuse, scattered growth or it can be clustered only locally and look like a small ground glass nodule. In general, most diffuse growths are benign lesions, and focal growths tend to be something bad. In the early stage, pulmonary nodules are often pure, low density, round-faced, and well-defined, which are not necessarily malignant, and can be called pure membranous glass nodules, which Chinese doctors like to call GGO. (100%, even in extreme cases it may be microinvasive adenocarcinoma (MIA), which invades <5 mm of the surrounding vascular stroma and does not metastasize, and after resection, the 5-year survival rate is 100%). Of course, when it grows progressively worse, it may cause an increase of solid component and become less pure, called mixed GGO; sometimes, there are also changes such as lobulation, burr, vacuoles, pleural depression, and dense blood vessels, and most of them are already malignant by then, called invasive adenocarcinoma. It can enter the human blood vessels and develop intrapulmonary or systemic metastasis. As you can see, the five-year survival rate of early-stage lung cancer can reach nearly 100%, while the five-year survival rate of late-stage lung cancer is only 4%! That's why it is so important to detect, diagnose and treat lung cancer at an early stage.