Under normal circumstances, axillary lymph nodes with a long diameter of 5mm or less, currently 10mm x 5mm, are abnormal. There are more causes of axillary lymph node enlargement, mainly seen in lymphadenitis, lymphoma, leukemia, malignant tumor lymph node metastasis and autoimmune diseases. 1. Lymphadenitis: It is mostly seen in bacterial or viral infectious diseases around armpit, breast and upper limb, such as mastitis, skin infection of upper limb, etc., which can lead to axillary lymphadenitis, manifested as swelling of axillary lymph nodes, pain, fever and other symptoms. 2. Lymphoma or leukemia: it can invade the axillary lymph nodes and cause enlargement. It can be diagnosed by puncture biopsy and bone marrow examination. 3. Lymph node metastasis of malignant tumors: the common malignant tumors with axillary lymph node metastasis are breast cancer, lung cancer, etc. The axillary lymph nodes may be enlarged in the presence of primary lesions. 5. Autoimmune diseases: the more common ones are systemic lupus erythematosus, rheumatism, etc., which can also lead to axillary lymph node enlargement. After the discovery of axillary lymph node enlargement, you should consult the doctor in time, complete the examination, and follow the doctor’s instructions to be treated accordingly after the diagnosis is clear.