What is the most common type of pain under the left breast?

Pain and discomfort in the left side of the chest due to trauma, seen in emergency surgery, cardiothoracic surgery.
For non-traumatic left-sided chest pain and discomfort, see cardiovascular medicine if you feel pressure-like pain in the left side of the chest with symptoms such as heartburn.
If there is dyspnea or coughing, you should consult a respiratory physician.
If you have breast lumps, nipple discharge or breast pain, wait until you see a breast surgeon.