The most common causes of enlarged lymph nodes in the mediastinum include the following: 1. Infectious diseases, most commonly pneumonia, and severe pneumonia can cause enlarged mediastinal lymph nodes; 2. Diseases of the lymphatic system itself, or diseases of the blood system itself, such as malignant lymphoma, Hodgkin’s disease, and non-Hodgkin’s disease, can cause enlarged lymph nodes. However, it will mainly manifest in the enlarged anterior lymph nodes, such as the enlarged lymph nodes in the neck; 3. Malignant tumors of the lung, which will also cause the enlargement of lymph nodes, for example, two lobes of the lung will cause the enlargement of lymph nodes in the mediastinum. Therefore, the way to deal with it is firstly to determine the specific cause of lymph node enlargement by lymph node biopsy and then to treat it.