Polythelia, the medical term for having one or more extra nipples, is not dangerous in the vast majority of cases. Extra nipples are one of the most common minor birth variations, affecting up to 6% of the population in the United States. Most people with an extra nipple will never experience any health problem because of it, and many don’t even realize what the small mark on their skin actually is.
That said, there are a few situations where an extra nipple deserves attention. Understanding what polythelia is, how it forms, and what to watch for can help you decide whether yours needs a closer look.
What Polythelia Is and Why It Happens
Around day 35 of fetal development, two ridges of tissue form along the front of the body, running from each armpit down to the groin. These are called the milk lines, or mammary ridges. In most pregnancies, nearly all of this tissue disappears except for two spots on the chest that become the nipples. When a small segment of the milk line doesn’t fully dissolve, the leftover tissue can develop into an extra nipple.
This is why extra nipples almost always appear somewhere along that armpit-to-groin line, most commonly just below the normal breast. They can also show up on the abdomen, and in rare cases near the groin or underarm. The trait runs in families. The most common inheritance patterns are autosomal dominant with incomplete penetrance (meaning a parent can carry and pass on the gene without necessarily having the trait themselves) and X-linked dominant transmission. Polythelia is more common in men than in women, though researchers aren’t entirely sure why.
What an Extra Nipple Looks Like
Extra nipples vary widely in appearance. Some look almost identical to a regular nipple, just smaller. Others are so subtle they’re mistaken for a mole, a birthmark, or a skin tag for years. In its simplest form, polythelia is just a nipple with no surrounding areola or breast tissue underneath. That distinguishes it from polymastia, which involves actual glandular breast tissue and is a different, less common condition.
If you have a small, round, slightly raised spot along your milk line that has always been there, it could be an extra nipple. A dermatologist can usually confirm the diagnosis with a visual exam.
The Kidney Connection
For decades, researchers have debated whether extra nipples signal a higher risk of kidney or urinary tract abnormalities. A study published in the Scandinavian Journal of Urology and Nephrology found that among children with known kidney or urinary tract problems, 6.62% had extra nipples, compared to just 1.09% in the control group. That’s a statistically significant difference, and it led the researchers to recommend that children with extra nipples be screened for urinary tract issues.
This association remains somewhat controversial. Not every study has confirmed it, and having an extra nipple certainly doesn’t mean you have a kidney problem. But for parents who notice an extra nipple on a newborn or young child, it’s reasonable to mention it to the pediatrician. A simple ultrasound can rule out any structural issues with the kidneys or urinary tract.
Hormonal Changes and Extra Nipples
Even a nipple without glandular tissue beneath it can respond to hormonal shifts. During puberty, pregnancy, or breastfeeding, extra nipples sometimes become more noticeable. They may darken, swell slightly, or become tender. In some cases, an extra nipple that was barely visible since birth suddenly becomes obvious during the third trimester of pregnancy as hormone levels surge.
These changes are not dangerous. They simply reflect the fact that the tissue is hormonally responsive, just like normal nipple tissue. The swelling and sensitivity typically resolve after pregnancy or once hormone levels stabilize.
Cancer Risk in Extra Nipple Tissue
This is the concern that brings most people to the search bar, and the answer is reassuring. Pure polythelia, meaning a nipple without any underlying breast glandular tissue, carries an extremely low risk of cancer. There’s essentially nothing there to become malignant.
The risk picture changes slightly when extra breast glandular tissue is present, which is a different condition called ectopic breast tissue or polymastia. Cancer arising in ectopic breast tissue accounts for only 0.2% to 0.6% of all breast cancers, making it very rare even in that scenario. When it does occur, it behaves like breast cancer in the normal location and is treated the same way.
The practical takeaway: if your extra nipple is flat or slightly raised with no lump or thickening underneath, the cancer risk is negligible. If you ever notice a firm mass, discharge, or a change in the skin around the extra nipple, that warrants evaluation, just as it would with a normal nipple.
Other Associated Conditions
Polythelia has occasionally been reported alongside other developmental variations. One documented association is with dental anomalies, particularly missing teeth (tooth agenesis). Both conditions appear to involve disruptions in genes responsible for organ development during early embryonic life. These associations are uncommon, and most people with extra nipples have no other developmental differences at all.
Removal: When and Why
Most extra nipples never need to be removed. The two main reasons people choose removal are cosmetic preference and diagnostic uncertainty. If a spot looks ambiguous and could be something other than an extra nipple, excision allows the tissue to be examined under a microscope. The procedure is straightforward, typically done under local anesthesia in a clinic, with minimal scarring and a short recovery.
If your extra nipple doesn’t bother you and isn’t changing in size, shape, or texture, there is no medical reason to have it removed. It’s a normal anatomical variant, not a medical condition that requires treatment.