The incidence of lung cancer is still increasing in recent years.In 2002, the incidence of lung cancer was the highest among Chinese men, accounting for 20.4%, and among women, it was second only to gastric cancer, accounting for 14.8%.In 2005, the literature reported that the incidence of lung cancer in China was the fourth highest in the world, with the incidence rates of 42.4/100,000 and 19/100,000 for men and women, respectively, and the actual number of incidence was the highest in the world. The actual incidence rate is the highest in the world. It is important to recognize the pre-invasive lesions of lung cancer for clinical research. The most common types of lung cancer are squamous carcinoma and adenocarcinoma. The incidence of adenocarcinoma of the lung has increased in both China and North America, and is now the most common type of lung cancer. Atypical squamous epithelial hyperplasia has been considered as a precursor to squamous lung cancer, and the World Health Organization (WHO) has suggested that the precursor to adenocarcinoma of the lung is atypical adenomatous hyperplasia (AAH). Lung adenocarcinoma is mostly seen around the lung fields. The increasing popularity of chest CT has improved the detection rate of peripheral type lung lesions, and regular follow-up has become a common diagnostic strategy for small nodules in the lung, which offers the possibility to improve the detection rate of pre-invasive lung adenocarcinoma. Definition of AAH: AAH refers to a lesion that is not associated with a primary lung cancer lesion, presents as a single row of non-invasive atypical epithelial cells lining the alveolar wall, is a mild to moderate limited hyperplasia of atypical cells, and can lead to focal lesions in the peripheral alveoli when the respiratory fine bronchi are involved, usually ≤5 mm, and is free of interstitial inflammatory and fibrotic changes. Factors associated with the occurrence of AAH Statistics show that the incidence of AAH varies among specimens: the incidence of AAH in resected lung cancer specimens ranges from 9.3% to 21.4%, while the incidence of AAH in lung specimens resected for other reasons ranges from 4.4% to 9.6%. The incidence of AAH is higher in women than in men. The incidence of AAH in multiple lung cancers is higher than that in solitary lung cancers. Some studies have reported that AAH may be associated with a history of previous malignancies, such as rectal cancer, liver cancer, breast cancer, thyroid cancer, head and neck cancer, and malignant lymphoma. In addition, the correlation between AAH and smoking history and family tumor history is still inconclusive and needs further study. The histological criteria for the diagnosis of AAH are: 1) clear lesion margins with a single layer of atypical epithelial cells and no atrophy or scar formation in the center; 2) abundant cell pulp, round or dome-shaped cells, similar to alveolar type II epithelial cells; 3) darkly stained nuclei with prominent nucleoli, less atypical than adenocarcinoma; 4) alveolar septa lined with atypical square or columnar cells, and mild fibrous thickening of alveolar septa. It should be noted that the diagnosis of AAH cannot be made by cytology. AAH is usually found in adenocarcinoma of the lung, especially multiple adenocarcinoma, and imaging of multiple adenocarcinoma is the only way to detect “suspicious” AAH. X-ray chest radiographs are less likely to detect AAH, High-resolution CT of the chest shows small, round-like lesions with clear borders and faint to moderate density, in the form of uniform hairy or frosted glass shadows with low translucency that do not obscure the underlying lung parenchyma, mostly less than 5 mm in size. GGO is not a specific imaging presentation of AAH. 30% of GGO surgical specimens are benign lesions, 10%-77% are AAH, 50% are adenocarcinoma in situ, and 10%-25% are invasive adenocarcinoma. It is noteworthy that most of the AAH occurred at the same time as the lung cancer (91.7%) and a few were heterogeneous, which suggests the importance of careful exploration during serial readings and surgery. In peripheral lung adenocarcinoma, fine nodules on other sites should be used as targets for surgical exploration and postoperative follow-up. Treatment and prognosis of AAH AAH is usually found in surgical resection specimens of lung cancer, and it is possible to avoid lung cancer by resection. The presence of AAH does not affect the prognosis of lung cancer surgery. 137 of 1360 surgically resected lung cancer cases in 1997 were associated with AAH, and no significant effect of AAH on the 5-year survival rate of all stages of lung cancer was observed. In recent years, the development of small incision surgery and thoracoscopic surgery has reduced surgical trauma. For small lesions near the chest wall that can be reached by minimally invasive surgery, if lung cancer cannot be excluded by examination, treatment can be decided accordingly, which may be beneficial for improving prognosis. Although there is no clear conclusion on whether isolated AAH that is not lung cancer should be surgically resected, minimally invasive surgery is worthwhile if the patient has high risk factors for lung cancer and cancer cannot be excluded.