8 years old baby girl left breast nucleus a little hard lump, clinical possible causes are early breast development, trauma formation of lumps, breast tumors and so on. 1. Early breast development: usually, the breast will first grow a breast nucleus when developing, this situation may suggest that the child’s breasts are beginning to develop, and touching the chest can be found in the breast there is a hard lump and accompanied by pressure and pain. However, this condition may belong to precocious puberty in 8-year-old children, and it is recommended to go to the hospital for treatment. 2. Lump formed by trauma: If the child has a lump found in the position away from the center of the breast, and there is also a history of trauma, it is usually considered that the local tissue edema may be formed due to trauma. 3. Breast tumor: this is extremely rare, and often occurs due to metastasis of tumors in other parts of the body and invasion of chest tissues. Parents are advised to go to the hospital as soon as possible for examination to make a clear diagnosis and take interventional treatment when their children are found to have this condition.