6-year-old children have a hard lump in the breast a little pain, common causes of mastitis, precocious puberty and so on. You should go to the hospital for a complete examination to clarify the cause of the disease and then target treatment, such as physical therapy, medication and so on. If mastitis is the cause of the above symptoms, the child will also be accompanied by localized skin swelling, redness, increased skin temperature, pain intensified by pressure and other symptoms. This kind of disease may be caused by poor hygiene habits for a long time, and should be treated with physiotherapy (such as topical compresses) and antibiotics (such as amoxicillin and ampicillin) in the hospital. Breast development caused by precocious puberty may also lead to the above symptoms, so the child needs to go to the hospital to test the gonadal hormone levels, check the breast ultrasound. Precocious puberty can lead to early closure of the epiphysis and lower lifelong height in adulthood, so the child needs to consult a doctor in time and be treated with drugs that inhibit the initiation of the gonads (e.g. leuprolide). There may also be other reasons for a hard lump in the breast of a 6-year-old child, so it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or therapy.