The incidence of lung cancer is still increasing in recent years, and 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%. 2005, it was reported in the literature that the incidence of lung cancer in China was the fourth highest in the world, with an incidence rate of 42.4/100,000 and 19/100,000 for men and women, respectively, which was the highest in the world. Recognition of pre-invasive lung cancer lesions is important 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 provides the possibility to improve the detection rate of pre-invasive lung adenocarcinoma. AAH is a focal lesion that is not associated with the primary lung cancer lesion, with a single row of non-invasive atypical epithelial cells lining the alveolar wall, which is a mild to moderate atypical cellular restrictive hyperplasia that can lead to focal lesions in the peripheral alveoli when the respiratory fine bronchioles are involved, usually ≤5 mm, and without 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%, and the incidence of AAH in lung specimens resected for other reasons ranges from 4.4% to 9.6%. -The incidence of AAH was also related to the type of lung cancer, with the incidence of AAH in adenocarcinoma ranging from 15.6% to 35.5%, higher than in other types, and in squamous carcinoma ranging from 3.0% to 11.0%. 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, single layer of atypical epithelial cells, no atrophy or scar formation in the center; ② abundant cytoplasm, round or dome-shaped cells, similar to alveolar type II epithelial cells; ③ deep stained nuclei, significant nucleoli, less atypical than adenocarcinoma; ④ alveolar septa lined with atypical cuboidal 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 lung adenocarcinoma, 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 well-defined borders and faint to moderate densities, in the form of uniform gross or frosted glass shadows (GGO) with low translucency that do not obscure the underlying lung parenchyma, mostly under 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 AAH occurs concurrently with lung cancer (91.7%), with a few being heterogeneous, suggesting the importance of careful exploration during serial readings and surgery. For peripheral type 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; in 1997, Suzuki et al. reported 137 cases with AAH among 1360 surgically resected lung cancer cases, and no significant effect of AAH on the 5-year survival rate of all stages of lung cancer was observed. The recent development of surgical small incision surgery as well as thoracoscopic surgery has reduced surgical trauma. For small lesions near the chest wall that can be reached by minimally invasive surgery, when lung cancer cannot be excluded by examination, treatment can be decided accordingly, which may be beneficial for improving prognosis. As to whether isolated AAH that is not lung cancer should be surgically removed, there is no clear conclusion, but if the patient is accompanied by high-risk factors for lung cancer and cancer cannot be excluded, minimally invasive surgery is worth performing. thv Imaging Park XCTMR.com