A lump in the breast in girls under the age of eighteen, especially those with a family history of breast cancer, is certainly a cause for concern. So what is the nature of these lumps? What tests are needed? How should they be treated? 1. Medical history: First of all, we should know the family history of breast cancer and whether the child’s chest has been treated with radiation. 2. Physical examination: Careful examination should be done to determine if the lump is a normal breast development or early childbirth, or if it is an accessory nipple and breast. Some people will have more than one breast or nipple on one side. Boys may also have temporary breast development (gynecomastia) around puberty. It usually goes away on its own. Imaging: Ultrasound can distinguish solid tumors from some cysts (lactocele), lymphadenomas, hemangiomas, abscesses, and cyst of Montgomery. Adults have the BI-RAD classification system (American College Radiology Radiology Imaging Reporting and Data System), which may not be suitable for use in the pediatric population. In the January 2016 issue of Ped Surg Int, an analysis of 113 cases of pediatric breast pathology concluded that the most common type of fibroadenoma in girls, accounting for 3/4 of the total, and several variants of fibroadenoma (juvenile, tubular, or more than 5 cm) were found. Juvenile, tubular or giant fibroadenoma. Others include adenomas, lipomas, neuroma, hamartoma, etc. Malignant breast tumors are extremely rare in children. Most of them are related to previous radiation exposure. Less than 50 cases have been reported in the world literature. Lobular cystic sarcoma (phylloides) is a subtype, most of which are benign and few are malignant. 5.How to deal with: (1) Observe for a period of time, about 1/3 or more of the fibroadenoma will become smaller or disappear. (2) Puncture biopsy and cytopathological examination can be done. (3) Selective excision of the mass for biopsy and case examination.