The incidence of lung adenocarcinoma is second only to that of squamous carcinoma, and statistics in recent years show that its incidence has increased significantly, and in some areas the incidence of the two has become comparable. The incidence of lung adenocarcinoma in women is relatively common, accounting for more than half of the cases. Adenocarcinoma of the lung usually occurs in the smaller bronchial epithelium, so most of them are peripheral type lung cancer. The mass is usually located under the pleura and is not well defined, often involving the pleura. Adenocarcinoma with fibrosis and scar formation is more common. The clinical treatment and prognosis of lung adenocarcinoma is not as good as that of squamous carcinoma, and the 5-year survival rate after surgical resection is less than 10%. The histological types of adenocarcinoma are mainly classified into in situ, microinvasive and infiltrative adenocarcinoma. In situ adenocarcinoma is a small adenocarcinoma that grows along the alveolar wall with no interstitial or vascular infiltration ≤ 3 cm, while microinfiltrative adenocarcinoma is a small adenocarcinoma that grows mainly in an isolated, adnexal manner with infiltrative foci ≤ 0.5 cm. Invasive adenocarcinoma with infiltrative foci >0.5 cm can be classified into 3 categories according to the degree of differentiation: highly, moderately and poorly differentiated. Highly differentiated adenocarcinoma mainly shows squamous growth of cancer cells along the alveolar wall, alveolar duct wall, and sometimes along the fine bronchial wall. The alveolar septum is mostly undamaged and the alveolar contour is still preserved. Moderately differentiated adenocarcinoma can be subdivided into subtypes such as glandular, papillary and solid mucinous cell type according to morphological features such as glandular ducts, papillae or mucus secretion, and the proportion of cancerous tissue. Hypodifferentiated lung adenocarcinoma usually has no glandular-like structure, solid striae, rare secretion phenomenon, and obvious cell heterogeneity.