Possible reasons for shortness of breath in patients with lung adenocarcinoma include: compression of trachea or main bronchial tube, extensive intrapulmonary dissemination, combined with serious lung infection, and formation of large amount of pleural effusion. 1. Compression of trachea: increasing tumor size of lung adenocarcinoma patients can cause compression of main bronchus or even trachea, leading to serious lung ventilation obstacle and shortness of breath. 2. Extensive intrapulmonary dissemination: lung adenocarcinoma can have extensive intrapulmonary dissemination, forming multiple metastatic foci in both lungs, which seriously destroys the lung tissues, leading to respiratory failure caused by a large reduction in the area of respiratory membranes, and then shortness of breath. 3. Combined with serious lung infection: tumor bleeding or blockage of bronchial tubes can easily cause lung infection, if not timely intervention may develop into large-scale lung infection and cause shortness of breath. 4. Formation of large amount of pleural effusion: when lung adenocarcinoma develops pleural metastasis, large amount of pleural effusion may be formed, which may seriously affect lung expansion and cause shortness of breath. The presence of cancerous pleural effusion indicates that the patient is in the advanced stage of cancer. Lung adenocarcinoma patients with shortness of breath are recommended to go to the hospital as soon as possible to find out the cause of shortness of breath and get appropriate treatment, so as to alleviate the symptoms of patients as much as possible and improve their quality of life.