The presence of swollen lymph nodes in the armpit may be due to lymphadenitis, lymphoma, lymph node tuberculosis, metastasis of malignant tumors and other reasons. It should be diagnosed and treated under doctor’s guidance. 1. Lymphadenitis: When bacterial or viral infection leads to axillary lymphadenitis, or when bacterial or viral infection occurs in the lymphatic drainage area of the axilla, the lymph nodes will be enlarged and have obvious pain when touching. 2. Lymphoma: Lymphoma can also cause axillary lymph node enlargement, which is a kind of malignant tumor originated from lymphohematopoietic system, and there can be chronic painless lymph node enlargement, and some patients can have axillary lymph node enlargement. 3. Lymph node tuberculosis: when the patient’s axillary lymph nodes are infected with tuberculosis bacillus, it may cause axillary lymph node enlargement. 4. Metastasis of malignant tumors: Lung cancer, breast cancer and other malignant tumors can cause axillary lymph node enlargement through lymphatic metastasis, which is usually manifested as hard texture of the enlarged lymph nodes, inconspicuous tenderness, poor mobility, and easy to be fused. In addition, some connective tissue diseases, such as tuberculosis, systemic lupus erythematosus, etc. can also lead to axillary lymph node enlargement. Patients with signs of axillary lymph node enlargement should actively improve the examination under the guidance of the doctor, and be treated accordingly after a clear diagnosis to avoid aggravation of the symptoms, which may cause serious consequences.