The adult female breast is a symmetrical, hemispherical sex organ located between the superficial and deep layers of the superficial fascia at the level of the second to sixth intercostal space in front of the thorax. The mammary gland is a type of sweat gland tissue that reaches to the parasternal bone, externally to the anterior axillary line, and externally to the axillary fossa in an angular pattern called the Spence’s axillary caudal area; it is important in the surgical excision of radical breast cancer, and the anatomical boundary must include the above-mentioned area during surgery. The central anterior projection of the breast is the nipple, and the surrounding pigmented area is the areola. Each breast contains 15 to 20 lobes and lobules arranged in a whorl pattern, the latter consisting of many vesicles; there are connective tissue intervals between lobes and between lobes and vesicles. The fibrous bundle between the lobes is called Cooper’s ligament, which is also called mammary suspensory ligament, which keeps the mammary gland in a certain degree of mobility. The milk ducts in each glandular lobe, which are connected to the alveoli, converge toward the nipple to form the lobular milk ducts, which gradually increase in size to form the pot belly and then divide into 6-8 openings on the nipple surface. The enlarged area of the large milk ducts forming the pot belly is the site of intraductal papillary cancer. When the milk ducts are lined with epithelial cells and their basal layer (germ layer) is significantly proliferated, different lesions can be formed, such as cystic hyperplasia and ductal carcinoma.