Having an extra nipple, or even multiple extra nipples, is a documented biological possibility. This condition is a relatively common congenital anomaly, meaning it is present from birth, and has a specific medical classification. The presence of one or more additional nipples is medically termed a supernumerary nipple, or polythelia when referring only to the nipple structure without underlying glandular tissue. This finding, while often surprising to the person who discovers it, is generally benign and represents a minor variation in human development.
The Medical Reality of Extra Nipples
The occurrence of supernumerary nipples is more common than many people realize, with studies estimating its prevalence to be in the range of 1% to 6% of the population. This makes it one of the most frequent developmental anomalies involving the breast tissue. The underlying biological cause is rooted in a process that occurs early in fetal development, during the fourth to fifth week of gestation. Two thickened strips of ectodermal tissue, known as the mammary ridges or “milk lines,” form bilaterally on the embryo, extending vertically from the armpit region down toward the groin. Normally, most of this tissue regresses, leaving only the small portion in the chest area to develop into the two typical breast structures. Polythelia results from the incomplete regression of these embryonic mammary ridges, allowing a small focus of this ectodermal tissue to develop into an extra nipple, an areola, or sometimes even a full accessory breast structure.
Where Extra Nipples Appear and How They Vary
Supernumerary nipples almost always appear along the path of the embryonic mammary ridge, which is the vertical line often referred to as the milk line. This anatomical track runs from the armpit, down the side of the torso, past the normal breast area, and ends near the inner thigh or groin. The appearance of these extra structures can vary significantly, ranging across a spectrum from a fully formed, miniature breast to a simple pigmented spot. At one end of the spectrum is polymastia, which involves a fully developed accessory breast with a nipple, areola, and underlying glandular tissue. This type can swell or lactate in response to hormonal changes, such as during pregnancy. More commonly, the extra structure is simpler and less developed, often mistaken for a mole or a birthmark. The most common type of polythelia is a nipple structure alone, without the surrounding areola or glandular material.
Are Supernumerary Nipples Linked to Other Health Issues?
For the vast majority of individuals, an isolated supernumerary nipple is a harmless finding that does not indicate any underlying systemic disease. However, the presence of polythelia has been the subject of debate regarding its potential association with other congenital anomalies, most notably those involving the urinary tract and kidneys. This discussion stems from the fact that the mammary ridge and the genitourinary system develop around the same time during embryogenesis. Some studies have reported an increased incidence of kidney and urinary tract abnormalities, including conditions like hydronephrosis or polycystic kidney disease. These reported associations suggest a shared developmental pathway that could be affected by a single genetic or environmental factor. In clinical practice, the concern is that an extra nipple could be a minor external marker for a more serious internal issue. Due to this historical and debated association, healthcare providers may recommend screening, often with a renal ultrasound, particularly if the supernumerary nipple is fully developed or if there are other accompanying congenital findings.
When and Why Are Extra Nipples Removed?
The management of supernumerary nipples is straightforward, as treatment is typically not medically necessary. Most individuals who choose to have them removed do so for elective and cosmetic reasons, or when the extra tissue causes physical irritation or discomfort. This is particularly true for more developed accessory breast tissue, which can swell, become tender, or even lactate in response to hormonal fluctuations during menstruation or pregnancy. The procedure is usually a noninvasive, outpatient surgery performed under local anesthetic. In rare instances, removal may be medically warranted if the tissue shows signs of developing pathology. Since accessory breast tissue is susceptible to the same diseases as normal breast tissue, including the formation of cysts, fibroadenomas, or cancer, surgical removal and biopsy are recommended if abnormal changes, lumps, or discharge occur.