Prolonged mild chest pain can be seen in blood diseases, pleurisy, esophagitis, coronary heart disease, breast hyperplasia and so on. 1. Blood disease: patients with blood disease such as leukemia, the abnormal proliferation of cells makes the pressure in the sternal cavity increase, thus leading to sternal pain. 2. Pleurisy: the pleura is located on the inner surface of the chest wall, if the pleura is infected, the stimulation of inflammation can also lead to chest pain. 3. Esophagitis: the esophagus is located behind the sternum, patients with esophagitis and esophageal ulcers may also experience chest pain. 4. Coronary heart disease: such as angina pectoris may occur when there is prolonged mild chest pain, accompanied by chest tightness, a sense of suffocation, and so on. 5. Breast Hyperplasia: Women with breast hyperplasia may also experience chest pain, which is more pronounced before the onset of menstruation. There are many reasons for prolonged mild chest pain, if prolonged mild chest pain can not be relieved, it is recommended to go to the hospital for further examination to clarify the cause of pain, symptomatic treatment, do not miss the condition.