Men before the left breast has a hard lump after no longer may be due to physiological factors, may also be due to pathological factors such as trauma, costochondritis, etc., should be timely consultation to identify the cause of the disease. 1. Physiological factors: some adolescent boys will secrete estrogen, when the body androgen secretion is insufficient, estrogen has a relatively large impact on the body, can occur unilateral or bilateral breast lumps, most of the normal physiological phenomenon, to the body androgen secretion is normal, the symptom can disappear on its own. 2. Pathological factors (1) Trauma: such as left chest muscle strain, mainly manifested as hardness or pain in the injured area, swelling, muscle tension, spasm, hard lumps may appear, and the hard lumps will disappear after recovery. (2) Costal chondritis: related to strain and trauma, the cartilage of the articular surface of the thoracic ribs is edematous and thickened, and aseptic inflammation occurs. There may be swelling and hardness at the rib cartilage, and the hardness may disappear after the inflammation disappears. As this symptom alone can not determine the disease, and do not rule out other factors. It is recommended that the patient consult the doctor in time, ask the doctor to clarify the cause of the disease, and give targeted treatment.