The article describes a clinical case of giant fibroadenoma in a 13-year-old girl, whose size was 20 cm, as well as a brief review of the scientific literature on benign neoplasms of the mammary glands in young patients. Giant fibroadenomas account for 0.5 to 2% of all fibroadenomas. In children and adolescents, ultrasound of the mammary glands is the main method of diagnosing fibroadenoma. Fibroadenoma needs to be differentiated from a phylloid tumor, which is clinically no different from fibroadenoma, but at the same time it has a high risk of malignancy. To make a final diagnosis, a puncture fine needle aspiration biopsy is additionally perform