Lateral chest pain near armpit is usually caused by lymphadenitis, parasthesia, membranitis, lung cancer and other diseases, and it can also be seen in female breast cancer. 1. Lymphadenitis: Lymphadenitis caused by infection will lead to enlargement of axillary lymph nodes and chest pain, which can be treated with anti-infective, antipyretic and analgesic drugs. 2. Paramastia: paramastia can cause chest side near armpit pain, treatment can be performed paramastectomy. 3. Pleurisy: in pleurisy, the friction between wall pleura and dirty pleura on both sides of chest wall is large, which can be manifested as pain on the side of chest near axilla. Tuberculosis pleurisy is more common in clinic, which usually requires regular anti-tuberculosis treatment. 4. Lung cancer: when cancer cells invade ribs and brachial plexus nerves, the symptom of pain on the side of chest near axilla will appear. 5. Female breast cancer: breast cancer can pull or invade the fascia of chest wall and cause axillary pain on the chest side, if there are indications for surgery, surgery is recommended. If there are indications for surgery, surgery is recommended. It is recommended to go to the hospital for further diagnosis and treatment of chest pain near the armpit.