Causes of enlarged lymph nodes include infection, tumor, immune disease hyperplasia and so on. 1. Infection: it is a common cause of lymph node enlargement. Pathogenic microorganisms (viruses, bacteria, Mycobacterium tuberculosis, parasites, etc.) cause local inflammation, which can stimulate lymphoid follicle proliferation, and the center of follicle proliferation may be necrotic, forming abscesses, which will lead to lymph node swelling with pain. 2. Tumor: It is also a common cause of lymph node swelling, including lymphoid tissue tumor and non-lymphoid tissue tumor. The former refers to malignant tumors originated from lymphocytes, including lymphoma, lymphocytic leukemia, etc., which proliferate continuously and lead to enlarged lymph nodes. Non-lymphoid tumors are tumors of other tissues and organs, mostly malignant tumors metastasized to lymph nodes, proliferating continuously and causing lymph node enlargement, such as thyroid cancer, breast cancer, lung cancer, intestinal cancer and so on. 3. Immune disease hyperplasia: it can be seen in systemic lupus erythematosus, tuberculosis, etc. Due to the stimulation of immune substances, it can cause lymph node hyperplasia and enlargement. It is recommended to consult a doctor in time for standardized treatment under the guidance of a professional doctor when lymph node enlargement occurs.