Estimates vary, but most clinical studies place the prevalence of supernumerary nipples (the medical term for extra nipples) somewhere between one and five percent of the general population. The spread depends heavily on how carefully examiners look and what they count, because many third nipples are so small or faintly formed that they pass for moles or birthmarks for an entire lifetime. The condition is more common in men than in women by roughly a 2-to-1 margin in most surveys, though nobody has a convincing explanation for why.
Why the Numbers Are So Uncertain
If you search for a single authoritative percentage, you will find a frustrating range. Some older studies from the 1970s and 1980s reported prevalence around one to two percent in European and North American hospital populations, while surveys of neonates in Hungary and Japan found rates closer to five or even six percent. The gap is not random. Studies that relied on routine physical exams tended to report lower numbers because small, flat supernumerary nipples are easy to miss during a quick check-up. Studies where clinicians specifically looked for extra nipples on every patient found considerably more of them.
Population also matters. Surveys in some East Asian populations have reported higher rates than those in European cohorts. Whether this reflects a genuine genetic difference or simply more thorough screening practices is still debated. The honest summary is that a figure around one in fifty people (roughly two percent) is a reasonable middle estimate, but if you include the smallest, most subtle forms, the true number could be double that.
What a Third Nipple Actually Looks Like
Most people picture a fully formed nipple sitting somewhere on the chest, but the reality is far less dramatic. The most common type is a small, slightly raised bump that looks a lot like a mole, consisting of nipple tissue alone with no areola or glandular tissue underneath. A clinical classification system published by Kajava in 1915 still used today describes eight distinct types, ranging from a complete extra breast with nipple, areola, and glandular tissue all the way down to just a patch of hair marking the spot where a nipple might have been.1DermNet. Supernumerary nipple
The full spectrum includes:
- Complete: a nipple with areola and underlying glandular breast tissue, essentially a small extra breast
- Nipple only: the most common form, often mistaken for a mole or skin tag
- Areola only: a pigmented circle of skin without a raised nipple
- Glandular tissue only: no visible surface marking, just breast tissue under the skin
- Hair patch only: a localized tuft of hair along the milk line with no other nipple features
Because the nipple-only variant is so common, many people discover they have a third nipple only after a dermatologist or doctor identifies it during an unrelated exam. The bump tends to be small, flesh-toned or slightly darker, and is sometimes slightly textured differently from surrounding skin. It rarely looks like the two nipples you already know about.
The Milk Line and Why Extra Nipples Show Up Where They Do
During early embryonic development, a ridge of tissue called the mammary ridge (or milk line) forms on each side of the body, running from the armpit down the front of the torso to the groin. In humans, most of this ridge regresses before birth, leaving behind just one pair of nipples on the chest. When a small segment of the ridge fails to disappear on schedule, the result is a supernumerary nipple.
This is why extra nipples almost always appear along a predictable vertical line on the front of the body, most commonly just below the normal breast or on the upper abdomen. They can show up higher too, near the armpit, or lower, near the navel or even in the groin area, though those locations are rarer. Occasionally a supernumerary nipple appears outside the milk line entirely, on the back, shoulder, or thigh. These off-line cases are genuinely unusual and tend to attract more clinical curiosity because they do not fit the standard embryological explanation neatly.
Having one extra nipple does not necessarily mean you will have just one. Some people have two, three, or more, though having more than two extras is uncommon. The extras can appear on one side of the body or both.
Are Third Nipples Inherited?
There does seem to be a hereditary component. Supernumerary nipples sometimes cluster in families, and clinicians have long noted that a parent with an extra nipple is more likely to have a child with one. The pattern does not follow a simple single-gene model in most cases, though. It appears to involve multiple genes interacting with developmental timing, which is why it can skip generations or appear unpredictably.
In some rare genetic syndromes, supernumerary nipples are a recognized feature rather than an isolated finding. Simpson-Golabi-Behmel syndrome, an overgrowth condition primarily affecting males, includes extra nipples alongside tall stature, distinctive facial features, and heart defects.2American Journal of Medical Genetics. Clinical and molecular aspects of the Simpson-Golabi-Behmel syndrome Another example is AEC syndrome (ankyloblepharon-ectodermal defects-cleft lip/palate), where supernumerary nipples appear alongside fused eyelids, skin abnormalities, and cleft palate.3PubMed. The syndrome of ankyloblepharon, ectodermal defects and cleft lip and palate: an autosomal dominant condition These syndromic cases are quite rare, and the vast majority of people with a third nipple have it as an isolated trait with no associated health problems.
The Kidney Question
For decades, a persistent clinical belief held that people with supernumerary nipples were significantly more likely to have underlying kidney or urinary tract abnormalities. This idea traces back to a 1979 proposal by a Hungarian geneticist named Méhes, who argued that the embryonic tissues giving rise to nipples and kidneys were developmentally linked, so a disruption in one system could signal a disruption in the other.
The evidence for this association has been mixed and often weaker than the original claim suggested. A study of 65 patients with supernumerary nipples who underwent kidney imaging found that about 11 percent had a significant kidney abnormality, but the researchers noted that the association was “significantly weaker” than Méhes had originally proposed. They also found that the link appeared to vary by race, with no renal defects found in Black patients with supernumerary nipples in their sample.4PubMed. Does a supernumerary nipple/renal field defect exist?
Later studies produced conflicting results, and most current pediatric guidelines do not recommend routine kidney imaging just because a newborn has an isolated extra nipple. The consensus has shifted toward viewing kidney screening as warranted only when there are other suspicious findings, not when the extra nipple appears alone in an otherwise healthy baby. If you were told as a child that your third nipple meant you should have your kidneys checked, that advice reflected an older, more cautious standard.
Can a Third Nipple Develop Cancer?
When glandular breast tissue underlies a supernumerary nipple, that tissue is theoretically susceptible to the same diseases that affect normal breast tissue, including cancer. Documented cases of breast cancer arising within supernumerary nipple tissue exist in the medical literature, but they are rare enough to be published as individual case reports rather than studied in large cohorts. One case involved a 62-year-old woman who carried a BRCA-1 gene variant and had a history of breast cancer in her normal breast; she later developed a new primary cancer within a supernumerary nipple even after undergoing surgical risk reduction on her primary breasts.5PubMed Central. Implications of a Supernumerary Nipple Breast Cancer in a BReast CAncer Sequence Variation Carrier: A Case Report
Because these cancers are so uncommon, no formal screening guidelines exist specifically for supernumerary breast tissue. The practical advice from clinicians is straightforward: if you have an extra nipple and you notice it changing, growing, becoming painful, or developing a lump beneath it, get it examined. A high degree of suspicion for any nodule or thickening on or near the milk line is warranted, and biopsy should be considered for anything that changes or becomes symptomatic.6JAAD Case Reports. Invasive ductal carcinoma arising from an accessory nipple: A case report and review of the literature For most people with a simple nipple-only variant and no underlying glandular tissue, cancer risk from the extra nipple itself is essentially not a concern.
Hormonal Responses and Pregnancy
Because supernumerary nipple tissue can contain functional glandular components, it sometimes responds to the same hormonal shifts that affect normal breasts. During pregnancy, some people notice that an extra nipple they had barely been aware of becomes more prominent, darker, or even tender. In rare cases involving significant underlying breast tissue, supernumerary nipples have been reported to produce milk during lactation. This can be startling if you never realized the bump was anything more than a mole, but it is a normal physiological response of breast tissue to pregnancy hormones.
Hormonal changes during puberty can similarly make a previously inconspicuous supernumerary nipple more noticeable. The tissue may enlarge slightly, darken, or develop sensitivity that mirrors what happens in the primary nipples. These changes are not dangerous, but they sometimes prompt the first visit to a doctor about a bump that had been present since birth without drawing attention.
When a Third Nipple Gets Mistaken for Something Else
One of the most clinically relevant aspects of supernumerary nipples is how often they get misidentified. Dermatologists have noted that under dermoscopy (the magnified skin examination tool used to evaluate moles), accessory nipples display network-like structures that can closely resemble a melanocytic lesion, the kind of pigmented growth that raises concern about melanoma.7PubMed Central. Dermoscopy of accessory nipples This resemblance has led to unnecessary biopsies and excisions when the “suspicious mole” was simply an extra nipple all along.
Knowing the dermoscopic features that distinguish an accessory nipple from a true melanocytic lesion helps clinicians avoid these unnecessary procedures. The location is an important clue: a pigmented bump sitting directly on the milk line, particularly below the breast, should prompt consideration of a supernumerary nipple before jumping to biopsy. That said, if there is genuine uncertainty, removing and examining the tissue is always the safer call.
Removal and Psychosocial Considerations
Most third nipples require no medical treatment. They are benign, painless, and functionally inert. Removal is typically considered for one of two reasons: cosmetic preference or a clinical concern about the tissue underneath.
Cosmetically motivated removal is more common than you might expect. Congenital anomalies affecting appearance can meaningfully affect body image and self-esteem, particularly during adolescence when appearance-related self-consciousness peaks. Research on similar congenital cosmetic differences, including chest wall deformities, has found that dissatisfaction with appearance can substantially reduce quality of life. In case reports of supernumerary nipple excision, patients have described improved confidence and satisfaction following the procedure, suggesting genuine psychosocial benefit even when there were no physical symptoms to address.8International Journal of Surgery Case Reports. Isolated supernumerary nipple along embryonic milk line in an adult male patient successfully treated by surgical excision: a case report
The procedure itself is usually straightforward. For a nipple-only variant with no underlying glandular tissue, a simple excision under local anesthesia is standard. Recovery is quick, and the scar is typically small. When significant breast tissue is present, the surgery is slightly more involved but still considered a minor procedure in most cases. Insurance coverage varies; many plans classify purely cosmetic removal as elective, while removal prompted by symptoms, diagnostic uncertainty, or cancer risk may be covered.
The Witch Trials Connection
Supernumerary nipples have a darker place in history than most people realize. During the Salem witch trials and earlier European witch hunts, examiners searched accused individuals for physical marks believed to be signs of a pact with the devil. “Witch’s marks” were described as raised or flat skin lesions, sometimes pigmented, that were believed to serve as teats from which demonic familiar spirits would suckle. Historians and dermatologists have concluded that these witch’s marks were most probably supernumerary nipples.9PubMed. Role of skin lesions in the Salem witchcraft trials
“Devil’s marks,” a related category of evidence used in the trials, encompassed a broader range of skin findings including red, blue, or brown lesions with unusual outlines. But the witch’s marks specifically, those said to provide sustenance to animal-shaped agents of the devil, align closely with what we now understand as extra nipples or areolar tissue along the milk line. Given that several percent of the population carries these marks, an accusation supported by a physical exam had a disturbingly good chance of turning up “evidence.” The trials effectively pathologized a common, harmless anatomical variant and turned it into proof of supernatural evil.
Famous People and Pop Culture
Third nipples have gotten an unusual amount of attention in popular culture, partly because several celebrities have publicly acknowledged having one. Mark Wahlberg’s supernumerary nipple on his left chest became one of the more widely known examples in the 1990s, though he later had it removed. The condition also shows up in fiction: the James Bond villain Scaramanga in “The Man with the Golden Gun” is identified partly by his third nipple, a plot device that made the trait seem exotic and villainous rather than mundane.
The pop-culture framing tends to treat third nipples as either a curiosity or a punchline, which can skew public perception. In reality, the trait is common enough that most doctors encounter it regularly and treat it as unremarkable. The fascination says more about how unusual people assume it is than about anything medically interesting about the trait itself. If you have one, you are in the company of roughly one in every twenty to fifty people, depending on whose estimate you trust, and the overwhelming majority never need to do anything about it.
Third Nipples in Other Mammals
Humans are not the only species where nipple count varies. In fact, supernumerary nipples are much easier to understand when you consider that most mammals have multiple pairs of nipples as their default. Dogs typically have eight to ten, cats have six to eight, and pigs can have twelve or more. The human norm of just two nipples is already an evolutionary reduction from the ancestral mammalian pattern. A third nipple in a human is, in a developmental sense, a partial reversion to the more typical mammalian arrangement rather than a bizarre anomaly.
This evolutionary framing explains why extra nipples are so common and why they almost always appear along the milk line. The genetic and developmental machinery for producing nipples at multiple points along that ridge is ancient and highly conserved across mammals. All it takes is a small variation in the signaling that tells the mammary ridge to regress, and one or more extra nipples persist. It is not a defect so much as a variation in the degree to which an ancestral trait gets suppressed during development.