Lung adenocarcinoma is a type of lung cancer and belongs to non-small cell carcinoma. Unlike squamous cell lung cancer, lung adenocarcinoma is more likely to occur in women and non-smokers. It originates from the bronchial mucosal epithelium, and a few originate from the mucous glands of large bronchi. The incidence rate is lower than that of squamous cell carcinoma and undifferentiated carcinoma, the age of onset is younger, and it is relatively more common in women. Most adenocarcinomas originate from smaller bronchi and are peripheral lung cancers. There are generally no obvious clinical symptoms in the early stages, and they are often discovered during chest X-ray examinations. They appear as round or oval masses, which generally grow slowly, but sometimes blood metastasis occurs in the early stages. Lymphatic metastasis occurs later.