The breast includes glands, ducts, adipose and fibrous connective tissue, nerves, blood vessels and lymphatic vessels. The breast is divided into 15 to 25 lobes, each of which is divided into several lobules, each of which is composed of 10 to 1,000 vesicles. The number and size of lobules varies greatly from person to person, and varies from person to person at different times. Each lobule is like a small tree buried in fat and growing upside down, and the “leaves” at the top of the tree are the follicles of the breast, where milk is produced after childbirth, and then the milk flows from the “leaf stem” (small milk ducts) to the “trunk” (milk ducts). trunk” (the milk duct). The terminal ducts near the alveoli, alveolar ducts and alveoli are the main sites of cystic hyperplasia and breast cancer. The milk ducts are narrower at the nipple and expand inward to become the sinus of the milk duct, which serves as a storage site for milk and is the most common site for intraductal papillomas.