There are many reasons that cause vague pain in the left chest of men, such as heart disease, costal neuritis, breast hyperplasia and so on. 1. Heart disease: myocardial ischemia often occurs due to a temporary imbalance between myocardial oxygen demand and oxygen supply, and patients may have pain in the precordial area and the left upper extremity. After using nitroglycerin or resting, the symptoms are relieved. 2. Costal neuritis: Inflammatory reactions are often triggered in the intercostal space due to various reasons, such as viruses and trauma. The most prominent symptom of intercostal neuritis is pain, which is often aggravated by deep breathing or sneezing. 3. Breast hyperplasia: patients are often caused by a transient increase in endogenous estrogen or a decrease in androgens, diffuse breast hyperplasia, often with swelling, tingling, throbbing pain. There may also be other causes, for example, left-sided pleurisy can also lead to chest pain, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment.