With the development of medical science and the advancement of examination methods, especially the widespread use of CT, small lung nodules, which were difficult to detect by X-ray in the past, have been discovered. Unfortunately, some people mistakenly believe that lung nodules are lung cancer. In fact, lung nodules and lung cancer are not equivalent. There are benign and malignant lung nodules, most benign lung nodules can be left untreated and untreated, and some of the lung nodules are malignant, mainly lung cancer. So, what should be done if a lung nodule is found by chance during physical examination or other tests? How should they be treated? Most benign lung nodules can be left untreated The lungs are the body’s organs for gas exchange, and a person has to inhale a large amount of air every day. As people grow older, nasal and bronchial hairs slowly decrease and their ability to secrete mucus decreases, and air pollution, dust and various microorganisms in the air exceed the person’s defense ability and enter the lungs, leading directly to bronchitis, pneumonia, emphysema and other lung diseases. Sometimes the amount of dust and microorganisms that enter the lungs is small and confined to a certain local area, and with the patient’s strong resistance, many phagocytes are mobilized to engulf them and produce fibrous tissue to surround them, which is actually local inflammation of the lungs. Because it is predominantly a cellular proliferation, often called chronic inflammatory granuloma, such nodules are benign and often do not require any treatment. However, some dusts in the air, such as fumes from some factories, dust from interior decoration and smoke inhaled by people smoking, are themselves carcinogenic, and they can cause cellular genetic mutations that lead to the development of cancer. The lung nodules produced at this time may be malignant. Smokers not only inhale soot that is carcinogenic in itself, but also significantly impairs bronchial cilia and secretion functions, so the incidence of lung cancer is significantly higher in smokers than in non-smokers. Whether benign or malignant, lung nodules are usually asymptomatic when they are small, i.e., the patient does not feel them. The best way to detect lung nodules at present is to have a CT examination. So what if a pulmonary nodule is found incidentally during a physical exam or while doing other tests? As mentioned earlier, most benign lung nodules can be left untreated and untreated, and malignant lung nodules have a good prognosis as long as they are diagnosed accurately and treated promptly, but if they are misdiagnosed, the consequences can be serious. The difference between benign and malignant nodules as small as a soybean or a peanut meter is extremely subtle. How to accurately distinguish these subtle differences is the diagnostic evidence that doctors need to have. Finding and displaying these subtle differences requires a high level of examination technique. Once a pulmonary nodule is found, the patient should not panic, let alone ask for an operation before the diagnosis is clear, but most importantly, get the diagnosis clear first, preferably by going to a large hospital with conditions for detailed examination and asking an experienced doctor to make a diagnosis. This is a pseudo-proposition, just like “is water good or bad”, and the discussion is not clear. There is a duality in everything, and it depends on how you grasp it and apply it. The sun brings us all kinds of rays, visible rays, invisible rays, alpha rays, beta rays, gamma rays, infrared rays, ultraviolet rays, etc. X-rays are invisible rays, a small amount can diagnose and treat diseases, but a large amount can cause damage or even death. How much is harmless and how much is harmful? Studies have shown that less than 100msv (msv millisieverts, a unit of measurement for radiation) has no effect on the human body. A course of radiation therapy of at least 2000 msv, a low-dose CT of about 1 msv, and a conventional-dose CT of about 3-5 msv, show that the correct use of X-rays for diagnosis will not cause harm to people.