The presence of extra nipples, often referred to as third nipples, is a congenital anomaly. These additional features are typically benign skin variations, though they are frequently misunderstood or mistaken for moles or birthmarks. Medically known as supernumerary nipples, they represent a minor deviation in embryonic development and are a relatively common occurrence.
Defining Supernumerary Nipples
Supernumerary nipples are defined as additional instances of nipple tissue that form outside of the usual pair on the chest. This condition arises from the embryonic “milk lines,” which are thickened strips of ectoderm extending from the armpit area down to the groin during fetal development. While these ridges normally regress everywhere except the pectoral region, a failure of complete regression can leave behind remnants that develop into an extra nipple or associated tissue.
Classification
Supernumerary nipples are classified using the Kajava system, which categorizes them based on the anatomical components present, ranging from a complete accessory breast (polymastia) to a simple patch of hair. The location of these features is usually along the embryonic milk line, though they can rarely appear in ectopic locations. The most common form is polythelia, which is an extra nipple alone, without underlying glandular tissue. Polymastia involves accessory glandular tissue and is much rarer, meaning the extra tissue could potentially enlarge or even lactate during hormonal changes like puberty or pregnancy.
Prevalence and Statistical Frequency
The prevalence of supernumerary nipples is challenging to determine precisely, as reported statistics vary widely across different studies and populations. Globally, the prevalence is estimated to fall within a range of approximately 0.2% to 6% of the general population. This broad range is influenced by factors such as the study’s methodology, the age of the subjects, and the specific ethnic group examined.
Lower rates, such as 0.22%, have been reported in some white European cohorts, while other populations have shown frequencies as high as 5.6%. The incidence has been noted to be higher in African American neonates compared to white European populations, and one study reported a 5% rate in Japanese women. The variation in prevalence also stems from the difficulty of identifying the smallest and most incomplete forms, which may be overlooked or mistaken for skin blemishes.
The most common presentation is a single extra nipple, though some individuals can have multiple supernumerary nipples. Familial cases, where the condition runs in a family, are reported in about 6% of cases and often follow an autosomal dominant pattern of inheritance.
Medical Significance and Management
For the majority of people, the presence of a supernumerary nipple is a benign condition with no medical consequence. They are typically discovered incidentally during a routine physical examination and require no specific monitoring or treatment.
Because the mammary ridges develop during the same embryonic period as the urinary tract, there has long been a hypothesis regarding a potential association with kidney or urinary tract anomalies. Early studies suggested a link, but more recent research has largely failed to confirm a significant association in the asymptomatic population. Physicians may still inquire about a family history of renal issues, but routine imaging is generally not recommended for an otherwise healthy individual with an isolated supernumerary nipple. The presence of extra nipples may be one feature of a larger genetic syndrome, but in most cases, it is an isolated finding.
Management usually involves patient education and reassurance, as the condition is often a cosmetic concern rather than a health risk. Surgical removal is an option, usually performed for cosmetic reasons or if the tissue is bothersome. Removal to rule out rare pathology, such as a potential for malignancy in glandular tissue, is sometimes considered.