Supernumerary nipples are common minor congenital malformations that consist of nipples and/or related tissue in addition to the nipples normally appearing on the chest. Supernumerary nipples are located along the embryonic milk lines. Ectopic supernumerary nipples are found beyond the embryonic milk lines. The embryonic milk line is the line of potentially appearing breast tissue as observed in many mammals. In humans, the embryonic milk line extends bilaterally from a point slightly beyond the axillae on the arms, down the chest and the abdomen toward the groin. It is generally thought to end at the proximal inner sides of the thighs, although supernumerary nipples have been described on the foot. Supernumerary nipples can appear complete with breast tissue and ducts and are then referred to as polymastia, or they can appear partially with either of the tissues involved.
The classification established by Kajava in 1915 remains valid :
Although this classification is clear, encountering interchangeable terms and misnomers when dealing with the supernumerary nipple complex is not surprising due to variability in morphologic patterns.
The paucity of descriptions of supernumerary nipples in medical writings is probably due to its relatively minor clinical significance. The occurrence of supernumerary nipples has been documented since Roman times and featured in legends and ethnic mythology prior to that time. Supernumerary nipples, and particularly polymastia, were attributed to increased femininity and fertility. Ancient artists depicted the goddess of Artemis of Ephesus and the Phoenician goddess of fertility, Astrate, like other ancient deities, as having row upon row of breasts on their chests. Anne Boleyn, the wife of King Henry VIII, was known to have a third breast. Supernumerary nipples in men were a sign of virility and endowed them with divine powers. Nowadays, film stars expose their supernumerary nipples in the cinema with this same effect.
The first medical report dates back to 1878 when Leichtenstern estimated the prevalence of supernumerary nipples to be 1 in 500 (0.2%). In recent years, supernumerary nipples and their association with other congenital anomalies and malignancies has been a topic of considerable debate.
Supernumerary nipple features are found in a number of syndromes, but, in most cases, it is probably a chance finding. These syndromes include Turner syndrome, Fanconi anemia, and other hematologic disorders ; ectodermal dysplasia; Kaufman-McKusick syndrome; Char syndrome; Simpson-Golabi-Behmel syndrome; and epibulbar lipodermoids associated with preauricular appendages syndrome. Isolated reports have linked supernumerary nipples to a number of other conditions, but in light of the fact that supernumerary nipples occur with a relatively high frequency in the general population, further studies are needed to validate the following associations:
Central nervous system associations are as follows:
Gastrointestinal associations are as follows:
Ears, nose, throat, and lung associations are as follows:
Skeletal associations are as follows:
Cardiac associations are as follows:
In 1979, Méhes drew attention to the association of supernumerary nipples and other anomalies. The claim that 40% of supernumerary nipples investigated also had renal involvement was striking. This figure was later corrected to 23-27%[8, 9] ; however, more recent studies have not validated this association. In addition to renal and urinary tract malformations, supernumerary nipples have also been reported in association with solid organ malignancies such as renal adenocarcinoma, testicular cancer, prostate cancer, and urinary bladder carcinoma.
Claiming close association are as follows:
Denying support for association are as follows:
The Medscape article Disorders of the Breast may be of interest.
Saint-Hilaire in 1836 and Darwin in 1871 supported the notion that the supernumerary nipple is an atavistic structure derived from the milk line of mammals. Conceivably, even the ectopic supernumerary nipple falls in line with Darwin's theory of atavism. Supernumerary nipples on the vulva are consistent with the location of breasts in dolphins and whales; whereas, ectopic supernumerary nipples on the back, scapula, and shoulder[32, 33, 34] are reminiscent of breast tissue in nutria and hutia (rodents).
Between the fourth and fifth weeks of embryogenesis, an ectodermal thickening forms symmetrically along the ventral lateral sides of the embryo. This epidermal ridge extends from the axillary region to the inner side of the thigh to form the embryogenic milk (or mammary) line. During the second and third months of embryonic development, the glandular elements of the breast are formed near the fourth and fifth ribs, with regression of the rest of the thickened ectodermal streaks. In the case of failure of a complete regression, some foci may remain, resulting in a supernumerary nipple. This can develop into a supernumerary complete breast (polymastia) or into any other supernumerary nipple variant according to the Kajava classification.
The prevalence of supernumerary nipples varies geographically. The prevalence is 0.22% in a Hungarian population, 1.63% in African American neonates, 2.5% in Israeli neonates, 4.7% in Israeli Arabic children, and 5.6% in German children.
The incidence of supernumerary nipples is similar in males and females. Some studies have supported a slight male predominance with estimates of male-to-female ratio as high as 1.7:1.
Most isolated supernumerary nipples persist without complication. Ectopic breast tissue can be associated with the same inflammatory and neoplastic conditions that affect normal breast tissue. Ectopic breast tissue does not have an increased malignant potential compared with normal breast tissue.
Once a supernumerary nipple is diagnosed, inform the parents or the patient that it is a benign skin lesion in an otherwise healthy individual. Patients should be made aware that supernumerary nipples can go through changes like any regular nipple or breast; these changes may be physiological during puberty or pathological, such as inflammation, mastitis, abscess formation, cysts, adenomata, fibroadenoma, carcinoma, melanoma, or Paget disease.
The supernumerary nipple typically remains asymptomatic and undetected. Occasionally, the supernumerary nipple becomes apparent during puberty, menstruation, or pregnancy when hormonal changes result in increased pigmentation, swelling, tenderness, or even lactation.
The supernumerary nipple is often overlooked at the first examination of the neonate. It appears as a small pigmented or pearl-colored mark or as a concave or umbilicated lesion.
Supernumerary nipple in a neonate. Courtesy of Dr P. Merlob.
In 75% of patients, it measures no more than 30% of the diameter of the normal nipple (at times no more than 0.2-0.3 cm in diameter). In the other 25% of patients, it is as large as 50% of the normal size of the nipple. Rarely, a supernumerary nipple is as large as a normal nipple.
Supernumerary nipple in an adolescent boy. Courtesy of Dr B. Fisher.
Most supernumerary nipples are single. Multiple supernumerary nipples may be present and as many as 8 have been reported in the same individual. When multiple supernumerary nipples are present, they may be distributed bilaterally or unilaterally, symmetrically or asymmetrically. Most supernumerary nipples are located inferior to the normal nipple, while approximately 13% appear above it along the milk line.
When examining adolescent girls (note the image below), the normally developed breast may hide the supernumerary nipple. A number of studies have indicated a preponderance of supernumerary nipples on the right side.
Supernumerary nipple (bilateral) in an adolescent girl.
For easier detection of the supernumerary nipple, a wet gauze pad is passed along the mammary line (milk line) from the axillary region to the upper part of the thigh on each side. This technique is particularly helpful in the dry and desquamating skin of full-term and postterm infants. When the suggested lesion is concave, folding it between fingers shows a typical wrinkling.
A dermoscopic examination of supernumerary nipple shows a pattern similar to the dermatofibroma with a central, white, scarlike area and a peripheral fine-pigment network. The supernumerary nipple may also present with a cleftlike appearance centrally in the absence of lateral pressure, thus allowing differentiation from dermatofibroma. For a more precise examination one can resort to a reflectance confocal microscopy.
Approximately 5% of supernumerary nipples are identified in ectopic locations outside of the milk line, such as on the back, shoulder (note the image below), extremities, neck, face, genitalia, and perineum.
Ectopic supernumerary nipple on the shoulder. Courtesy of Dr B. Fisher.
Most supernumerary nipples are sporadic, although familial cases have been reported, including 1 report of a family who had supernumerary nipples in 4 successive generations. Familial cases are typically inherited in an autosomal dominant fashion with incomplete expressivity.
The histologic features of a supernumerary nipple are identical to that of the regular nipple, including hyperpigmentation, slight hyperkeratosis with epidermal thickening, pilosebaceous structure of Montgomery areolar tubercles, smooth muscle bundles typical of the areola, and possible mammary glands and intradermal straight ducts. A significant increase in the number of clear cells of Toker has been found in supernumerary nipple tissue, and some authors have proposed that the supernumerary nipple may be a precursor of extramammary Paget disease.
Cosmetically undesirable or symptomatic supernumerary nipples should be removed with complete surgical excision, although the use of liquid nitrogen cryotherapy has been described. The removal of polymastia or a complete ectopic supernumerary nipple (with breast) is more involved but is indicated in women at high risk of developing breast cancer. To avoid an unsightly scar after the removal of a complete ectopic supernumerary nipple, the tumescent liposuction technique has been suggested.[44, 45]
The Medscape Dermatologic Surgery Resource Center may be of interest.
The presence of a sporadic supernumerary nipple in an otherwise healthy individual is typically not an indication for a thorough workup for other malformations. Exceptions are a supernumerary nipple accompanied by additional minor malformations, a prominent ectopic supernumerary nipple, or an established familial supernumerary nipple. Physical examination and mammography of ectopic breast tissue should occur at the frequency recommended for normal breast tissue in a particular patient.