There are many causes of pain in the chest and armpit junction, as follows: 1. costochondritis, common in women, mostly due to prolonged exertion caused by cold or weight bearing, need to take anti-inflammatory drugs to reduce inflammation or closed with lidocaine treatment. 2. bronchitis, manifested as cough, coughing sputum, runny nose, sore throat and pain in the chest and armpit, can be treated with erythromycin anti-infection, while using cough and phlegm analgesic drugs. 3. 3. Breast enlargement, the patient will have breast swelling and stabbing pain before and during menstruation, and the pain will disappear at the end of menstruation. If the pain is severe, there will be involvement pain, leading to pain in other parts of the body.4. Breast cancer, cancer patients with cancer cells invading nerves will have breast pain, and if there is lymph node metastasis, it will lead to swollen and painful lymph nodes elsewhere, which needs to be treated immediately in hospital.