The 8-year-old girl has a large breast and a small breast, usually caused by physiological factors, but also may be the symptoms of breast disease. 1. Physiological factors (1) bad lifestyle: refers to the development of breasts during the period of development due to the underwear is too tight or sleeping posture is not correct, resulting in unbalanced development of the breasts, thus appearing in the case of a large and small breasts. This is a normal physiological phenomenon and does not require treatment. (2) Pubertal development: If the sensitivity of both breasts to hormones is different during pubertal development, it will also lead to the symptom of large and small breasts. 2. Breast disease: mainly 8-year-old girls with breast disease, when the breast appears red, swelling, heat, pain and other symptoms, should be considered to have acute mastitis. If an 8-year-old girl’s breasts appear for a long time, she should go to the breast surgery or general surgery department of the regular hospital in time for breast ultrasound and other examinations to clarify the specific causes.