Underarm lymphatic pain may be caused by lymphadenitis, breast hyperplasia, malignant tumor and other reasons. 1. Lymphadenitis: axillary lymph node pain is first considered to be the cause of lymphadenitis, lymph node inflammation, in addition to pain, but also can be manifested as the surface of the lymph node redness, swelling, fever and other acute inflammatory manifestations, the nature of the lymph nodes can be identified through the physical examination and ultrasound examination. 2. Breast hyperplasia: patients with breast hyperplasia may also show reactive axillary lymph node enlargement, and these lymph nodes will be enlarged and painful when estrogen secretion is exuberant. Especially in the pre-menstrual period, the symptoms will be more obvious, is a symptom accompanied by breast hyperplasia. 3. Malignant tumors: many malignant tumors such as breast cancer can metastasize to the axillary lymph nodes, resulting in pain due to the swelling of lymph nodes and compression of local nerves, which will be manifested as axillary lymphatic pain. Patients with symptoms of axillary lymphatic pain can go to the hospital as soon as possible for CT or ultrasound examination, and under the guidance and advice of doctors for proper treatment.