A hard disk in the chest is due to physiologic or pathologic causes. 1. Physiological factors: If the adolescent in the adolescent breast inside a disk-shaped hard lump, is the development of the breast nucleus, is the beginning of the development of the mammary gland at the beginning of a hyperplasia phenomenon, with the development of the process of smooth and disappear, do not have to worry too much. 2. Pathological factors: (1) breast hyperplasia: breast hyperplasia is mainly related to endocrine disorders, patients will feel breast pain, tissue hyperplasia, can be manifested as a hard disk inside the chest. (2) Breast fibroma: Breast fibroma is a common benign tumor, which manifests as a hard disk inside the chest with regular shape, smooth surface and good mobility. (3) Breast cancer: Breast cancer may be related to heredity, poor diet and other factors, and may manifest as a hard disk inside the chest with unclear boundary, irregular shape and relatively poor mobility. A hard disk in the chest should also consider mastitis, breast trauma and other causes, patients should seek medical treatment as soon as possible to clarify the cause and follow the doctor’s instructions.