A supernumerary nipple, often referred to as a “third nipple,” is a relatively common congenital anomaly. This condition involves the presence of an extra nipple or associated tissue on the body, in addition to the two typical nipples. It represents a minor developmental variation present from birth.
Prevalence of Supernumerary Nipples
The occurrence of supernumerary nipples varies across studies and regions, with prevalence rates ranging from approximately 0.22% to 6%. For instance, studies have reported rates of 0.22% in Hungarian populations and white Europeans, while reaching 1.63% in African American neonates and up to 5.6% in German children. In the United States, estimates suggest that up to 6% of the population may have a supernumerary nipple.
Appearance and Types
Supernumerary nipples can manifest in various forms, ranging from a small, mole-like bump to a more complete structure resembling a typical nipple. These extra nipples most commonly appear along the “milk line,” an embryonic ridge extending bilaterally from the armpits down through the chest and abdomen to the groin area. However, they can occasionally occur in other locations on the body, such as the neck, back, or even the foot, which are termed ectopic supernumerary nipples.
These extra nipples are categorized into types based on the presence of nipple, areola, and glandular tissue. The most frequent type, polythelia, involves only the nipple without an areola or underlying breast tissue. In rare instances, a supernumerary nipple can include a full breast with glandular tissue, known as polymastia. Most often, these extra nipples are smaller and less developed than regular nipples, and they may even be mistaken for moles or birthmarks.
Associated Medical Conditions
For most individuals, a supernumerary nipple is a benign finding with no medical significance. However, they can be susceptible to the same hormonal changes and diseases that affect normal breast tissue. This means they can enlarge during puberty, become tender premenstrually, or even lactate, especially if glandular tissue is present.
While typically harmless, some historical reports link supernumerary nipples to kidney or urinary tract anomalies. Early studies suggested an association, though more recent research has not consistently validated this as a common link. Nevertheless, some studies indicate a higher frequency of urinary tract anomalies in individuals with supernumerary nipples, particularly in familial cases. Rare associations with other conditions, such as certain cardiac arrhythmias, epilepsy, or tumors, including breast cancer, have also been reported, but these are typically isolated occurrences and not a common concern.
Embryological Origin and Clinical Management
Supernumerary nipples originate during early embryonic development, specifically between the fourth and sixth weeks of gestation. At this stage, thickened strips of ectoderm, known as mammary ridges or “milk lines,” form along the embryo’s ventral side, extending from the armpit region to the inner thigh. While the glandular elements of the breast typically develop only in the pectoral region, a supernumerary nipple forms if these embryonic ridges fail to fully regress elsewhere along the milk line. This developmental remnant is usually benign and does not require medical intervention.
Clinical management of supernumerary nipples is typically straightforward. Most do not require removal unless they cause discomfort, symptoms like pain or lactation, or for cosmetic reasons. Surgical excision is a common, quick outpatient procedure with local anesthetic. Although rare, if the extra nipple contains glandular tissue, it can develop conditions similar to those found in normal breasts, such as cysts, fibroadenomas, or even breast cancer. Regular physical examinations can help monitor changes in the extra nipple tissue.