Lung cancer makes people talk about cancer. Past data show that about 50% of lung cancer patients are already in advanced stage when they are diagnosed, losing the chance of radical surgery, and there is no possibility of cure for these patients. Thus, the key to lung cancer treatment is early diagnosis and early treatment. As people’s awareness of health and health care increases, their awareness and vigilance of lung cancer are getting stronger and stronger, and early diagnosis and early treatment of lung cancer are getting more and more attention, which makes the cure of lung cancer possible. How to diagnose lung cancer at an early stage? Many people think that there are always symptoms of lung cancer, and it is not too late to go for examination after the symptoms appear. Typical symptoms are coughing, coughing up sputum, blood in sputum or blood shreds, and further aggravation may lead to hemoptysis, chest pain, chest tightness, shortness of breath, hoarseness, even headache, vomiting, bone and joint pain. However, it is too late to go for examination when symptoms appear, and lung cancer at this time is mostly in the middle and late stages, and the treatment effect is extremely unsatisfactory. We advocate proactive health concept and prevention, regular health checkups are crucial, but the checkups need to be targeted, otherwise it is still difficult to achieve the purpose. For example, we advocate doing CT instead of ordinary chest X-ray. Ordinary chest X-ray is not easy to see the early lesions of smaller lungs because of the superposition of anterior and posterior lung tissues, septal angle, septal angle of ribs, apex of the chest and other blind areas, but also may miss the larger lesions in the blind areas, which cannot achieve the purpose of early diagnosis. Regular chest CT examination: With the rapid development of CT technology and the application of lung cancer screening, the detection rate of lung grinding glass density shadow, the early imaging manifestation of lung cancer, is gradually increasing and is being paid more and more attention. Ground glass density shadow of lung is manifested as a faint or mild increase in density in a certain part of the lung, which does not obscure pulmonary vascular texture, and is seen in various lesions such as inflammation, edema, hemorrhage, fibrosis and tumor. The majority of ground glass nodular neoplastic lesions found by pathology are mainly adenocarcinomas, bronchoalveolar carcinomas and atypical adenomatous hyperplasia. Since these lesions are often well differentiated carcinomas or precancerous lesions, early diagnosis and early treatment are of great interest. Pathologic basis and morphologic features of ground glass density shadow. Lung density is composed of four factors: the density of the air spaces in the lung, the density of the intrinsic lung tissue, the amount of extravascular fluid in the lung, and the volume of pulmonary blood. Therefore, any disease that causes changes in these factors will definitely cause changes in lung density and lead to the formation of ground glass density shadow. As long as the air content of the lung parenchyma decreases, the cell density increases, and the alveoli and terminal air sacs are partially filled with gas due to the proliferation of columnar cells in the alveolar wall, and the alveoli are not completely atrophied, a pulmonary ground glass shadow can appear. Thus, it is a characteristic but non-specific sign that can appear in a variety of pathological states such as tumor cell infiltration, partial exudation of lung tissue, inflammatory interstitial thickening, edema, and fibrosis. According to its distribution, it can be divided into central and peripheral types. The central type of ground glass density shadow is mainly distributed along the bronchovascular bundle in the middle and inner zone of the lung, with blurred borders, often accompanied by interstitial lesions such as abnormal bronchovascular bundle, honeycomb shadow and lobular septal thickening. It is currently the most advanced lung examination method, which can use high-resolution CT to accurately display the morphological and anatomical changes of the lesion; and also provide the metabolic characteristics of the tumor. This has helped to improve the malignancy diagnosis rate of ground glass density shadow. with the introduction of HRCT, the thin layer high resolution image of the whole lung has become a reality, and the sensitivity and specificity of the evaluation of ground glass-like density foci has improved significantly. With the increasing application of HRCT in clinical practice, the advantages of determining the pathological nature of lesions, determining the treatment plan and judging the prognosis of diseases through the morphological characteristics such as the size of ground glass density shadow on HRCT have become more and more obvious. The 1024 high-definition CT that has emerged in recent years is an excellent tool for diagnosing small pulmonary nodules and ground-glass shadow, and its scanning speed is extremely fast. This makes it possible to distinguish the nature of smaller lesions earlier and more accurately and to formulate the next step of diagnosis and treatment precisely. The smallest nodule was confirmed to be a lung cancer less than 5 mm. Glassy density images are mainly seen in small bronchoalveolar carcinoma and adenocarcinoma, which is a subtype of lung adenocarcinoma, and small peripheral lung adenocarcinoma <2 cm in diameter is divided into 6 subtypes according to tumor growth pattern. Type A refers to bronchioloalveolarcarcinoma (BAC); type B refers to limited BAC with collapse of alveolar structures; type C refers to limited BAC with active fibroblast proliferation; type D refers to poorly differentiated adenocarcinoma; type E refers to tubular adenocarcinoma; and type F refers to papillary adenocarcinoma with compression and destructive growth. Up to 30% of nodules in the upper lobe of the right lung are more likely to be malignant if they are more than 1.5 cm in diameter or if they have a round-like morphology. Studies have shown that a ground-glass density shadow >15 mm in diameter, which is nodular in appearance, is more likely to be an aggressive adenocarcinoma. What should I do if I find a small nodule or ground glass shadow in my lung? Should I follow up or have a minimally invasive surgery for a ground glass shadow? Should I do a local or lobectomy? Is lymph node dissection necessary? Small, solitary, ground glass shadows usually do not require special management, and regular follow-up can help in the differential diagnosis. Inflammatory lesions may resolve on their own over several months (within 3 months) or may dissipate with anti-infective therapy. If the limited glassy lesion gradually increases in size or density during 3-6 months of follow-up, it may suggest malignancy, which can be clarified by CT-guided thoracentesis biopsy, followed by surgical treatment to remove the lesion. A solitary ground glass density shadow that is stable over several months of follow-up is also likely to be focal pulmonary fibrosis, focal fine bronchoalveolar carcinoma, adenocarcinoma, or atypical adenomatous hyperplasia. In addition, solitary ground-glass densities ≥ 10 mm in diameter with malignant signs or solid components are indicative of early adenocarcinoma or precancerous lesions, which should be biopsied to clarify the diagnosis and guide treatment. For mixed ground glass density shadow with solid component, malignancy is mostly considered, and lobectomy or thoracoscopic resection of ground glass density shadow is feasible. It is generally considered that non-resolving ground glass shadows larger than 0.7 mm in follow-up are more likely to be early lesions, and minimally invasive surgery is preferred. If the lesion is located on the surface of the lung, the lesion can be identified by finger touch or preoperatively by Hookwire localization, and the localized lesion can be removed directly. If the lesion is deep in the lung parenchyma and difficult to locate, the corresponding lung segment can be resected according to CT localization, and rapid frozen pathology can be performed. If benign lesions or atypical adenomatous hyperplasia are reported, local excision or a larger wedge resection is sufficient. For patients with intraoperative definite adenocarcinoma of the lung, thoracoscopic local resection is preferred for types A and B if no lymph node metastasis is sampled; lobectomy with lymph node dissection is preferred for types C, D and E. For patients with T1a, wedge resection is feasible, and for patients with T1b, segmental lung resection can be considered. The existing literature reports a 5-year survival rate of 98% to 100% for early stage lung cancer with simple ground-glass density shadow, so chemotherapy and radiotherapy are not required after surgery. The above results show that lung cancer is curable, but the key is early diagnosis and early treatment, and regular chest CT screening makes early diagnosis of lung cancer possible.