Breast cysts usually do not cause swollen lymph nodes under the armpit. Swollen lymph nodes are usually related to lymphadenitis, lymphoma and breast cancer, which can be relieved by medication and surgery. 1. Inflammatory reaction: for example, mastitis, lymphadenitis, etc. It is mainly related to infection with bacteria and virus. If it is determined to be caused by bacterial infection, cephalosporin and cefixime should be taken orally as prescribed by doctor; and regarding lymph node inflammation caused by viral infection, anti-viral granules should be taken orally or interferon should be injected for treatment, and the lymph nodes will be reduced naturally after the inflammation is eliminated. 2. Lymphoma: it is mainly divided into benign and malignant tumors. The symptoms of benign tumors are not obvious and can be cured after timely surgery; while malignant lymphoma needs to be surgically removed as soon as possible, and then radiotherapy should be taken to inhibit the cancer cells according to the individual’s condition. 3. Breast cancer: it belongs to malignant tumor of breast, and the tumor will spread through lymph nodes after enlargement, resulting in enlarged lymph nodes. If it is in early stage, it is recommended to perform breast-conserving surgery as soon as possible, and after surgery, radiotherapy, chemotherapy and other comprehensive treatments will be adopted according to specific conditions. In order to clarify the cause of swollen lymph nodes in the armpit, it is recommended to consult a doctor in time, and then analyze the cause through mammography and pathological biopsy, etc., and target treatment under the guidance of the doctor.