The increase of mediastinal lymph nodes may be caused by normal changes, benign diseases, malignant diseases and so on. 1. Normal changes: It means that some lymph nodes are slightly larger in diameter than the surrounding lymph nodes under physiological conditions, usually without any pathology, and regular review is sufficient. 2. Benign lesions: most often seen in the mediastinum or chest organs and tissues of inflammation, such as purulent pleurisy, mediastinal infectious diseases, pneumonia, lymphatic tuberculosis, pericarditis and other conditions, due to the presence of draining lymphatic vessels, which cause the mediastinal lymph nodes enlarged. 3. Malignant diseases: if the patient has lung cancer, lymphoma, etc., the mediastinal lymph nodes will be enlarged when the cancer cells have metastasized. If the mediastinal lymph nodes are enlarged, it is recommended that the patient should consult the doctor in time to clarify the cause of the disease and take active treatment.