A nipple that does not protrude but sinks inward is called nipple invagination. Nipple invagination (sunken nipples) is itself a breast deformity and in some cases is even an outward symptom of malignancy on the breast. Before puberty, female breasts do not develop and the nipples are small. After puberty, with the change of hormone level in the body and the onset of menstruation, the breasts start to develop and the nipples gradually increase in size and protrude. The nipples of unmarried women and women who are not pregnant are smaller, but they protrude out of the areola plane; if they are partially or completely below the areola plane, or even reverse the concavity and sink under the skin surface, resulting in a crater-like localization, this situation is nipple invagination (nipple indentation). It is important to note that some girls are shy about breast development, they wear tight underwear to tighten their breasts, or prematurely wear too small a bra size, the developing breasts will be squeezed and become flat; at the same time, poor blood circulation in the compressed breasts, insufficient nutrient supply, which affects the normal development of the mammary glands; nipples are also squeezed and sunken in the breast, forming nipple invagination (nipple indentation). The degree of nipple invagination varies from person to person, with the milder cases showing only varying degrees of nipple depression or retraction, which can protrude or squeeze out the nipple after stimulation. In the case of severe cases, the nipple is completely trapped in the areola and cannot be pulled out, crater-like, and often accompanied by secretions or odor. Inverted nipples, even when extruded, are generally smaller, often without a visible nipple neck, and are split. The incidence of nipple invagination in women is 1 to 2 percent, usually bilateral, or only on one side, and the degree of nipple invagination can vary, affecting the aesthetic appearance of the breast. The occurrence of nipple invagination is generally due to congenital development, with shortened ducts, some tissue fibrosis contractures, and poorly developed smooth muscle of the nipple. The main causes of nipple invagination are ductal shortening and tissue fibrosis contracture. Secondary nipple invagination (acquired nipple invagination) is caused by pulling of the nipple by pathological tissue in the breast or compression by bra or corset. It is often caused by inflammation, tumors and other diseases that invade the ducts, ligaments, and fascia of the breast, causing contraction of the invaded ducts, ligaments, and fascia; unreasonably tight bras or overly tight bras occur during adolescence, causing nipple invagination due to poor blood circulation in the tightly bound chest, resulting in poor breast development. The clinical performance of nipple invagination (nipple depression) not only hinders the beauty of the breast, hinders the function of breastfeeding, and local difficult to clean, the sunken part is easy to hide dirt and often cause local infection, breast ducts and the depression is connected, inflammation can spread to the breast and cause mastitis. The degree of nipple invagination (nipple depression) varies, from a receding nipple to a recessed nipple or even an overturned nipple in severe cases. The nipple can be divided into three degrees according to the different depths of nipple invagination: 1, once the nipple is partially invaginated, the nipple neck exists and can be easily squeezed out, the size of the nipple after squeezing out is similar to normal people; 2, two degrees the nipple is completely sunken in the areola, but the nipple can be squeezed out by hand, the nipple is smaller than normal and most of the nipple neck is not present; 3, three degrees the nipple is completely buried under the areola and it is impossible to squeeze out the invaginated nipple. Inverted nipples are very likely to cause diseases such as nipple areola inflammation and inflammation of the mammary glands. Severe nipple invagination leads to mucosalization of the invaginated skin with eczema. Bleeding and erosion can occur, forming chronic inflammation. The ducts of the mammary glands are connected to the invagination, and the inflammation can spread to the mammary glands and cause mastitis by retrograde infection. If the nipple inversion is not corrected in time, the inflammation is stimulated for a long time, resulting in the contraction of the breast ducts due to chronic inflammation, the nipple inversion is more serious, and a vicious circle is easily formed. The nipple inversion seriously affects breastfeeding. Whether the nipple is flat or invaginated, it is bound to affect the baby’s sucking, making breastfeeding difficult or impossible after delivery. On the other hand, the accumulation of breast milk due to the inability to discharge may cause secondary breast infection. The first of these is to make sure that you have a good understanding of the situation. The nipples are often pulled to make the nipples protrude, the milk ducts, fibrous cords and smooth muscles stretch and lengthen, and the nipples naturally and gradually bulge outward. However, this requires a longer period of time and is carried out gradually to obtain good results. 2. Suction therapy is similar to the principle of manual pulling, through the negative pressure suction device, causing pulling on the invaginated nipple to achieve the purpose of lengthening the ducts and fibrous cords of the breast. 3, surgical treatment (1) stent method nipple invagination correction So far, this method is the only surgical method that can retain the function of lactation, the sunken nipple through the wire fixed in the external stent, after 3 to 6 months of continuous pulling, to achieve the purpose of lengthening the nipple, correction of nipple invagination. It is suitable for patients with mild, moderate or severe degree of sunkenness. This method does not require an incision in the skin, does not destroy the breast ducts, can preserve the function of breastfeeding, and also does not affect the sensation of the nipple, and has a low recurrence rate. The disadvantage is that the treatment time is longer and may cause inconvenience in life. (2) Incisional nipple invagination correction This method can be used for women who have already given birth and are not considering breastfeeding in the future, or for patients with recurrent local inflammation and severe indentation deformity due to scar pulling. During surgery, the breast ducts are completely cut off, the sunken nipple is fully released, and a tissue flap is designed to fill the tissue defect at the nipple root to strengthen the support of the nipple. The incision method of nipple invagination correction can be completed in one stage of surgery and the treatment time is short. However, the incision method requires disconnection or partial disconnection of the breast ducts, which affects the postoperative lactation function; if the scar on the deep side of the nipple develops contracture, it will cause recurrence of nipple invagination. Fourth, prevention If nipple invagination is congenital, it is recommended that when the breast begins to develop, the nipple be lengthened by insisting on the manual pulling of the nipple every day. In general, this method can effectively correct mild to moderate nipple invagination. For severe nipple invagination, it can also provide some relief. For nipple invagination due to secondary causes, it is necessary to actively treat the primary cause, remove the cause of nipple invagination as soon as possible, and create conditions for surgical treatment.