Lymph nodes are distributed throughout the body and are important immune organs of the human body. They can be divided into superficial lymph nodes and deep lymph nodes according to their locations, and normal lymph nodes are mostly in the range of 0.2-0.5 cm and are often distributed in groups, with each group of lymph nodes collecting lymphatic fluid from the corresponding drainage area. Usually, unilateral axillary lymph nodes are enlarged, mostly due to acute inflammation of the drainage area, such as cellulitis and mastitis. The causes of bilateral axillary lymph node enlargement are as follows: 1. Systemic infectious diseases: When the body is infected by various pathogens, the axillary lymph nodes are prone to swelling, both acute and chronic infections can lead to this phenomenon, such as viral infections seen in infectious mononucleosis, AIDS, bacterial infections seen in tuberculosis, brucellosis, helminth infections seen in syphilis, leptospirosis, etc., protozoa and 2. Tumors: malignant tumors can metastasize to adjacent or distant lymph nodes via the lymphatic system, such as lung cancer and breast cancer metastasizing to axillary lymph nodes, and such enlarged lymph nodes appear as hard, fixed masses; 3. Non-infectious diseases: including connective tissue diseases, such as systemic lupus erythematosus, dry syndrome, nodular diseases, and hematologic diseases, such as acute leukemia, lymphoma, etc. .