A 12-year-old boy with a hard lump in his chest, accompanied by symptoms of pain, is a relatively common condition when boys enter puberty. As males enter puberty after development, the body’s hormone level rises, androgen rises slowly, estrogen rises significantly will lead to the development of the chest, there are hard lumps, pain symptoms. In 3-6 months will disappear, do not need medication, usually pay attention to maintain a happy mood, ensure sufficient sleep, reasonable combination of nutritious diet, do not stay up late to help the development of the body. If the hard lump persists for more than half a year and still exists, you need to go to the hospital to check the hormone level, and at the same time exclude testicular disease, adenopituitary tumor, adrenal gland disease, poor liver function and other causes of estrogen elevation, and then timely symptomatic treatment.