Lung cancer is currently the malignant tumor with the highest morbidity and mortality rate in the world, and due to the effects of smoking and air pollution, the number of lung cancer patients in China has increased rapidly in recent years. Since most lung cancer patients are already in the middle or late stage when they visit the doctor, the treatment effect is not ideal and the long-term survival rate is low, improving the early diagnosis rate of lung cancer is a problem we need to solve urgently. Early stage lung cancer is often manifested as small nodules in the lungs, therefore, we can effectively screen out early stage lung cancer as long as small nodules in the lungs are detected in a timely manner and differential diagnosis can be made. Lung nodule refers to a soft tissue lesion within the lung parenchyma that is round, clearly demarcated and less than 75px in diameter. Clinically, foci smaller than 75px in lung parenchyma are called nodules, foci larger than 75px are called masses, and nodules smaller than 37.5px are called small nodules, and nodules smaller than 5mm are called micronodules. The reason for such a definition is that the size of nodules is related to the benignness and malignant nature of the nodules, and foci larger than 75px are mostly malignant, while nodules that are even more tiny have a high possibility of being benign. The smaller nodules are more likely to be benign. Are lung nodules lung cancer? Just like Mr. Dai mentioned earlier, many people start to suspect that they have lung cancer once they find small nodules on the medical checkup report, which makes them highly nervous and seriously affects their work and life. So are these nodules really “bad”? In fact, the nature of lung nodules is various, benign ones include inflammatory pseudotumor, misshapen tumor, tuberculosis ball, granuloma, lung abscess, sclerosing hemangioma, fungal ball and so on, pre-cancerous lesions, such as atypical adenomatous hyperplasia, and the malignant ones may be primary lung cancer or metastatic lung tumors. Knowing the above common causes of lung nodules, we can find that small nodules in lungs are not necessarily lung cancer, and many benign diseases can also be manifested as small nodules. Doctors mainly judge the benign or malignant nature of small nodules according to the imaging characteristics of small nodules and dynamic changes, and the diagnostic accuracy rate of experienced doctors can reach more than 90% at present. How to distinguish between benign and malignant lung nodules? Lung nodules are benign and malignant, and the probability of malignant tumor is about 20%-40%, and the probability of malignancy increases with age, so the lung nodules found in the physical examination must not be ignored. According to the results of clinical statistics, the diameter greater than 25px single nodule in the lung, malignant lesions accounted for more than half. Why are more and more people being found to have lung nodules nowadays? The reason is that multi-row spiral CT has been commonly used in clinical diagnosis and treatment, health checkup and disease screening. According to the statistics of more than 8000 cases of chest CT physical examination in hospitals this year, the incidence of small lung nodules is as high as about 20% or more. As CT has the advantages that ordinary X-ray can not be compared, high resolution, and for the cross-sectional image, can avoid the ribs, spine, heart obstruction and clear observation of lung tissue. Low-dose spiral CT can minimize the radiation dose on the basis of providing imaging information, and is currently the best method for detecting lung nodules. In order to improve the differential diagnosis of lung nodules, the CT examination needs to describe the location of the nodule, its size, density, shape, calcification, and the presence or absence of lobes, burrs, and pleural indentations at the margins. Simply put, benign nodules have clear and smooth margins; whereas malignant nodules have irregular margins that appear to have short, thin burrs. For follow-up patients, it is also necessary to compare with the historical data to see if there is any change in the morphology of the nodule. If necessary, high-resolution CT can also be used for three-dimensional reconstruction of lung nodules to precisely calculate their density and volume. At present, Xinhua Hospital adopts the latest 256-row ultra-high resolution CT for three-dimensional reconstruction of lung nodules, which is able to assess the periphery and infiltration in detail, probe the internal structure of the nodule, evaluate the growth status of blood vessels, and calculate the time of volume doubling, so that the display of lung nodules is clearer and the diagnosis is more definite, and the early stage of lung cancer has nothing to hide. Who should beware of lung nodules? There are several types of people who should not take it lightly when small shadows or nodules are found in the lungs during physical examination, and they should actively undergo formal examination and timely treatment: (1) people over 40 years old; (2) long-term smokers or passive smokers; (3) people who have been in contact with asbestos or radioactive elements; (4) people with a history of pulmonary tuberculosis or chronic inflammation of the lungs for a long period of time; (5) people who have a personal history of tumors or family history of lung cancer, especially those with a family history of lung cancer. (5) People with personal or family history of tumor, especially family history of lung cancer; (6) People with nodule size over 25px, accompanied by changes such as burr-like, lobulated or pleural depression. What should I do if I find a lung nodule? With the increasing popularity of spiral CT, the detection rate of lung nodules is getting higher and higher. However, the causes of lung nodules are complex and the clinical manifestations lack specificity, so it is difficult for doctors to make a diagnosis. If a physical examination reveals small nodules in the lungs, don’t worry, it is not necessarily cancer; even if it is cancer, there is no need to be afraid because most of them are extremely early cancers, which can be completely cured with timely and appropriate treatment. For patients with benign possible or uncharacterized lung nodules, regular CT follow-up should be conducted in conjunction with the patient’s risk factors for dynamic observation so as to make timely diagnosis. For patients with lung nodules whose morphological manifestations are highly suspicious of lung cancer, fiberoptic bronchoscopy or CT or ultrasound-guided percutaneous puncture biopsy of lung nodules can be taken according to the different locations of the nodules for pathological diagnosis, and thoracoscopic minimally invasive surgical resection can be taken if necessary. Clinically, some patients with pulmonary nodules sent for pathological examination after surgical resection of the nodules often have localized cancerous changes, but due to timely treatment, the long-term postoperative results are very satisfactory. The hospital has routinely carried out preoperative CT-guided lung nodule localization combined with minimally invasive diagnostic and therapeutic techniques such as single-port thoracoscopic lung wedge and segmental resection, and has adopted minimally invasive surgical resection for patients with highly suspected malignant lung nodules, which can be sent to the hospital for rapid frozen section on the spot, and a report can be issued in 30 minutes, and the scope of further surgical resection can be decided according to the intra-operative pathology results. This makes the surgery for lung nodules more precise and less invasive, and the recovery time for patients is greatly reduced. In conclusion, once a patient discovers a small nodule in the lung, he or she should not be overly nervous, but should not be paralyzed either. He or she should actively consult a professional thoracic surgery and radiology specialist for a definitive diagnosis, and undergo formal further examination or timely surgical treatment.