The reasons for the absence of nipples on the breasts are as follows: 1. The complete absence of nipples is a congenital developmental problem, such as Poland syndrome, which manifests as unilateral mammary gland and pectoralis major muscle dysplasia, combined with the deformity of the upper limbs and fingers. We have encountered patients with Poland syndrome where the entire chest wall is flat and without nipples unilaterally, which is a congenital developmental problem; 2, nipple invagination, the nipple is normally convex because it is the opening of many breast ducts, but some patients have disproportionate development of breast ducts and mammary glands, so the nipple is sunken into the skin, like a crater, and looks as if there is no nipple; 3, nipple cut off after tumor 4, after breast reconstruction or breast reconstruction, no nipple reconstruction is done, and the reconstructed breast has no nipple; 5, trauma, such as burns, burns or cutting injuries resulting in missing nipples.