Congenital nipple inversion is mainly diagnosed during a wellness regular physical by a pediatrician or general practitioner as the patient approaches puberty. Many inverted nipples present in pre-pubescent patients will resolve spontaneously during puberty. They do not tend to cause any problems then and are usually observed until puberty/adolescence for resolution. If they do not resolve with puberty, they will often persist, and repair may be indicated for breastfeeding, psychosocial, or cosmetic reasons in adulthood. Many patients come for correction/ treatment when faced with lactational difficulties. To grade the inversion, digital manipulation is generally attempted. 

Pathological/acquired nipple inversion after puberty or breast development is more worrisome for malignancy or other abnormalities. This is generally associated with nipple discharge (serous/bloody), nipple erosion, or a breast lump. It is important to obtain a detailed personal and family history in both male and female patients of any breast malignancy, as well as any confounding trauma history to the breast or chest, as scarring and fat necrosis can mimic malignancy. The latter is not likely to result in nipple discharge.

An inverted nipple is a clinical diagnosis. Investigations like mammography, ultrasound, or ductoscopic evaluation can be done when inverted nipples are associated with discharge/ ectasia/ malignancy. Findings may include treatable causes like underlying masses or infections.

Inverted nipples can be either unilateral or bilateral; congenital or acquired. Schwanger classified them as ”umbilicated” if intermittently inverted and “invaginated” if permanently inverted.[5] The surgical classification used today was described by Han and Hong. They classified them into 3 grades according to the degree of fibrosis, the ease of manipulation, and the extent of damage sustained by the lactiferous ducts.[5][6]

• Grade 1 inverted nipples - These are called “shy nipples.” They have minimal or no fibrosis and demonstrate a soft-tissue sufficiency. The lactiferous ducts are normal, even with the retraction. These nipples are very amenable to manipulation and maintain projection for a considerable time, thus enabling breastfeeding easily, although initiation may pose some difficulty.

• Grade 2 inverted nipples – They demonstrate fibrosis of a moderate degree. On tissue examination, smooth muscle bundles are seen encasing the fibrous stroma. The milk ducts are retracted. The nipples can be pulled out but retract back soon after. Breastfeeding is possible, but the baby may have difficulty latching on to the nipple. The decision to lyse the fibrous bands surrounding the lactiferous ducts is individualized. Most of the cases do not need surgical correction.

• Grade 3 inverted nipples – The fibrosis seen is remarkable, and there is severe soft tissue deficiency. Lactiferous ducts are tiny, constricted, and retracted to a considerable extent. Histologically, the terminal ductal units are fibrosed and atrophied. These nipples cannot be pulled out and often mandate surgical correction. Breastfeeding is nearly impossible. These patients do experience a wide variety of associated problems like rashes, sore nipples, and recurrent mastitis.

Management mainly depends on the grade of inversion. Over the years, there has been a wide variety of surgical and non-surgical techniques utilized to treat nipple inversion with satisfactory and non-satisfactory results. Non-invasive/ conservative techniques were implemented mainly for grade 1 inverted nipples with considerable success and grade 2 with partial success. Invasive/ surgical procedures are primarily indicated for grade 3 and persistent grade 2 inversions. As such, no standardized technique has been implemented.

The conservative methods mainly involve using devices to create graded/sustained suction on the nipple-areolar complex to protract the nipple and maintain the protraction.

A technique of historic significance, introduced by Hoffman in 1952, involved placement of thumbs on opposite sides of the nipple over the areola with firm downward pressure on the breast to evert the nipple, while slowly moving away from the nipple. This repeated all around and multiple times would protract the nipple, but a study done in 1992 by Alexander et al. determined that not only is this not helpful in breastfeeding but may actually disrupt the lactiferous ducts, and this technique has hence been abandoned.[7]

Yukun et al. treated all grades of nipple inversion for 10 years utilizing a nipple retractor made from the hollow end of a single-use syringe, then eight holes were punctured for sutures crossing the base, and the height of the retractor depended on the sizes of the nipple-areola complex and breast volume. Two sutures were made to cross beneath the base of the nipple to elevate the nipple, and the hollow retractor was placed on the areola with the nipple and four ends of the sutures in the center. Sutures were then passed through the prefabricated holes on the retractor base and were fixed with knots and suitable tension. The retractor was worn for 3-6 months and then could be removed.[8] Grade 1 and 2 inversions were treated more successfully than grade 3, but a significant advantage described was the prevention of lactiferous duct injury and preservation of breastfeeding.

Suction devices in the form of shells, cups, nipple retractors, and extractors have also been marketed for use to be worn under clothing. They work by pulling the nipple into a small cup, thus stimulating and protracting it. But no study so far has proven their efficacy and long-term benefits. Scholten suggested piercing as a method of correction that preserves the breast function. This is done by piercing the base of the nipple and inserting a stainless steel barbell of a type employed in decorative body piercing.[9][10] Removal of the piercing 3 months later maintained the corrected position for a minimum period of 12 months.

Surgical methods are generally employed for grade 2 and 3 inversions. The fundamental principle on which the different surgical procedures are based is that of releasing fibrous bands and galactophorous ducts, adding bulk below the nipple, and filling up the dead space created inside to give the nipple support and avoid reinversion.[11][12] The ideal technique is a simple and reliable procedure that does not require multiple incisions or special bulky dressings and is associated with minimal scars and a low rate of recurrence or sensorial disorders.[13] They can be categorized as lactiferous duct preserving and lactiferous duct damaging procedures. Local anesthesia with superficial and deep infiltration of the nipple and areolar complex is normally adequate to carry out most of the procedures. The surgical techniques most widely utilized were the creation of dermal and dermoglandular flaps, endoscopic release, internal suture, and interposition of alloplastic and autoplastic materials.[14]

Morris Ritz et al. suggested a simple operative technique using two dermoglandular flaps. The inverted nipple is elevated using a skin hook. A perinipple "doughnut" of skin is de-epithelialized to a width of 3mm. Two longitudinal 1.5cm dermofibrous flaps are created attached to the nipple base. The nipple is elevated to its maximal length, and the ducts and fibrous tissue are teased out to release the nipple. A blunt dissector is used to create two tunnels in the deep tissue beneath the nipple, wherein the flaps are stitched at the nipple base fairly taut with 4-0 monocryl. The skin is closed with interrupted half-buried sutures. Sidewalls of grade 3 nipples are not closed and left to heal by epithelialization. A doughnut dressing with antibacterial ointment is used with the neonipple secured to the dressing with 4-0 silk for the first 5 days. This technique did not see any major postoperative events but allowed for a successful correction with a minimal, well-tolerated scar around the neonipple base. An advantage of this technique is the ease of revision correction in case of failure.[15]

Some surgeons report the two flap repairs can result in a gradual up/down tilt. Hence Huang proposed a method with three dermofibrous flaps that added more bulk to the reconstruction, provided a stable floor, and maintained the cylindrical nipple structure. It involved the creation of 3 "diamond-shaped" flaps at 2, 6, and 10 o'clock positions and placing them turned down through the tunnels, which creates a conjoined space under the nipple after releasing the fibrosis and retracted ducts. Sloughing of the partial skin over the dome was the only complication noted postoperatively in five study patients, and this healed by epithelialization without incident.[16]

A dissecting microscope was found to be advantageous by Sowa et al., where they attempted correction of grade 3 inversions.[17] Midline and Z-shaped microincisions on the nipple-areola complex were made, followed by counter-traction with sutures on the split areola. The surgical dissecting microscope was employed to identify translucent elastic ducts buried in the white fibrous connective tissue. Careful dissection with microsurgical scissors preserved the ducts, which were opposed after adequate nipple projection. Two opposite nipple-based areolar dermal Z flaps narrowed the base of the nipple. They also employed 2-syringe based traction device to exert an anteriorly directed force to maintain the nipple in the overcorrected position. Nipple sensation and the ductal function were well preserved as a dissecting microscope permitted atraumatic and precise dissection without injudicious disruption of lactiferous ducts.

Lee et al. proposed an internal suturing technique to close the soft-tissue defect, sometimes present after eversion. An inferior periareolar 5 to 7 o'clock incision was made, and a superior periareolar nipple flap was raised. A traction nylon suture was applied to the inverted nipple to guide the dissection of the fibrous bands and ducts. After release, the defect was obliterated by a superior and inferior 2- layer suturing of the internal sidewalls of the nipple together. This was a duct-damaging technique that the authors reported had high patient satisfaction and no residual inversion, but had implications on breastfeeding.[18]

To obliterate the defect, rib/auricular cartilage use has been described for severely inverted nipples or recurrent nipple inversion after primary correction. After the release of the lactiferous ducts and fibrous tissue, a platform is created by applying 2-3 nylon sutures. A cartilage graft harvested from the posterior aspect of the ear/rib is fashioned into 2 disks and sutured as a laminated graft and then introduced into the pocket. It is immobilized with a single horizontal mattress suture placed at the base.[19] This results in a projected nipple, but with a very unnatural feel. This is also a duct-damaging technique, and successful breastfeeding is very unlikely.

Differential diagnosis is especially important for acquired cases of nipple inversion. Clinical findings like erosion, inflammation, erythema, eczema, bloody nipple discharge, or a palpable subareolar mass may accompany nipple inversion. Malignancy of the breast, Paget's disease of the nipple, erosive adenomatosis of the nipple, florid papillomatosis, subareolar ductal papillomatosis, and breast eczema are the main differential diagnoses for acquired causes. Post-surgery changes, fat necrosis, fibrocystic disease, and Mondor's disease are other benign etiologies. Rare causes include syringomatous adenoma of the nipple, nipple leiomyoma, and Borrelia-associated lymphocytoma cutis.

An algorithm was developed by Olivaz-Maneyo and Berniz for the treatment of nipple inversions.[20] The algorithm takes into consideration the lactation wishes of the patient and the degree of severity of nipple inversion. Lactation wishes are particularly important to consider in detail, as the duct-damaging procedures may cause irreversible damage and result in a total inability to breastfeed in the affected breast.

Congenital nipple inversion is a generally benign condition. The prognosis depends on the grade of inversion and the treatment option chosen. Grade 1 inversions have seen a good prognosis with simple non-surgical conservative treatment methods. The establishment of successful lactation normally ensures long term correction. Grade 2 inversions have seen equivocal results with conservative methods. In cases of recurrence or no improvement, surgical correction can be considered after careful discussions with the patient regarding future lactation goals.

Inverted nipple correction is normally a very safe procedure. Patients most often experience swelling and sensitivity in the immediate postoperative period, which resolves uneventfully. Bleeding and wound infection are the most common surgical complications, though both are rare. Recurrence of nipple inversion is the most significant complication, and the greatest risk of recurrence is seen at 6 to 12 months postoperatively.

Postoperative care involves simple gauze dressing with a local antibiotic ointment. Patients should refrain from digital manipulation until complete healing ensures.

Breasts and nipples are an inherent part of the definition of feminity, in addition to functioning to allow breastfeeding. Nipple inversion can not only be functionally deterring to a patient but can have a huge impact on their confidence and self-perception. This can affect pre-teens, teenagers, and adults for varying reasons. Children will quickly realize their nipple(s) look different than their peers', and may become victims of bullying. As children mature and become sexually active adults, significant effects on intimacy can develop. Some patients are aware of, but not at all bothered by this condition. It is, therefore, important to determine the underlying motivations for a patient presenting for nipple correction. Are these the wishes of the patient, or is the patient feeling external pressure to undergo correction that they otherwise would not have taught is a question that should be addressed?

Nipple inversion is a condition with cosmetic and psychological implications for the patient, and it is best managed with an interprofessional team approach. The treating clinician should be mindful of the primary reason for the correction, whether it is the establishment of functionality or improving the physical appearance. Proper patient counseling regarding the condition, along with the available treatment options, helps them make an informed choice about their management. The most important distinction is between benign, congenital, nipple inversion, and malignancy. There should be a low threshold for the surgeon to obtain a biopsy or other intervention to ensure malignancy is not overlooked.