In general, nine-year-old girls with hard lumps in their breasts may be normal growth and development, or it may be due to sebaceous cysts, breast nodules and other pathological causes, if it is normal growth and development, observation can be, if it is a pathological cause, you can take medication or surgical treatment. 1. Normal growth and development: when the breasts develop, some girls will have the symptom of hardening on both sides, which belongs to normal growth and development and does not need to be treated, observation can be done. 2. Sebaceous cysts: If the hard lumps are caused by sebaceous cysts, you can use amoxicillin and other medicines as prescribed by the doctor for treatment. 3. Breast nodules: If a girl has a hard lump in her breast caused by a breast nodule, the condition is in the early stage, you can first observe the main, if necessary, you can follow the doctor’s advice to use drugs such as tamoxifen for treatment. If the nodule in a short period of time rapid growth, or malignant probability is higher, it is recommended to early surgical treatment. There are many causes of hard lumps in the breasts of nine-year-old girls, and it is recommended that parents bring their children to the hospital as soon as possible to find out the cause of the disease, and then targeted treatment.