Mediastinal lymph node enlargement after lung cancer surgery may be tumor metastasis or reactive proliferation of lymph nodes. Lung cancer can be metastasized through lymphatic or blood channels. Mediastinal lymph node enlargement after surgery of lung cancer patients may be due to tumor cells metastasizing to mediastinal lymph nodes and proliferating locally, resulting in lymph node enlargement. In addition, lung cancer may lead to reactive hyperplasia of mediastinal lymph nodes or inflammatory changes within the lymph nodes, which in turn cause lymph node enlargement. Once enlarged mediastinal lymph nodes are found, it should be clarified whether it is metastasis or inflammation as soon as possible. Generally speaking, it is possible to do puncture biopsy of enlarged lymph nodes under the guidance of bronchial ultrasound or surgical resection to take biopsy for pathological examination to clarify the nature of the enlarged lymph nodes and then adopt corresponding treatments, so those who find enlarged mediastinal lymph nodes after lung cancer surgery are advised to consult doctors in a timely manner.