By Diane Mapes

While many men and women have strong opinions about the size of breasts, most would agree the number of their breasts — two— is fine.

Unfortunately, for those with polymastia, that’s not always the case.

Sometimes referred to as accessory breasts, polymastia is the presence of supernumerary (extra) breasts on the human body. The extra breast tissue can appear in many forms, everything from a third nipple (the most common condition, referred to as polythelia) to a fully-formed — and fully-functional breast — in some unusual location on the body. It can also present itself as a breast with a nipple but no areola, a breast with an areola but no nipple, or just a small lump of breast tissue with neither nipple nor areola.

It’s not as rare as you might think, according to a recent article in The American Surgeon. Up to 6 percent of the general population has accessory breast tissue, although it is commonly misdiagnosed, usually as lipoma, a benign tumor composed of fat cells. In a few cases, supernumerary breasts can be diagnosed with breast cancer. Women report a much higher rate of polymastia and polythelia than men, but there have been several reported cases of men with accessory breast tissue. Extra nipples are more common.

Actor Mark Wahlberg has a third nipple, which he considered removing but eventually decided to keep. According to the blog, thesuperfluousnipple.blogspot.com (where “three is a magic number!”), other triple nippler guys include Jackson Browne, Brian Jones of The Rolling Stones, Frank Langella, and the fictional characters Krusty the Clown (“The Simpsons”) and Chandler Bing of “Friends” (Chandler had his superfluous nipple surgically removed).

Much less common (and less celebrated, perhaps) are the cases of men with fully-formed accessory breasts. In 1980, the Journal of American Academic Dermatology reported the highly unusual case of a 74-year-old man with a normal female breast on the back of his left thigh. According to the article, he told researchers he’d had the “fatty tumor” almost all his life and it had “never caused a problem.” He also refused to have his accessory breast removed.

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In women, supernumerary breasts and nipples are usually found on the embryonic mammary or “milk line,” i.e., the ridge that extends from the armpit to the groin. Famous female supernumeraries include the Greek goddess Artemis. More recently, Tilda Swinton, Lily Allen and comedienne Moms Mabley have owned up to sporting a spare nip.

According to Dr. Anne Burdick, professor of dermatology at the University of Miami, Miller School of Medicine, the most common location for accessory breast tissue is in the axilla (or armpit).

“The extra breast tissue is usually in one armpit or the other, but it can exist in other areas, as well, including the mid-chest, the sternum, the back, or even in the genital area,” she says.

Indeed, cases of aberrant breast tissue have been reported on the back of the neck, the buttock, the vulva, the hip, the shoulder, the perineum (the region between the anus and the genitals) and the mid-back. A 1997 article in the Journal of Pediatric Surgery describes an incident of supernumerary breast tissue on the face (it was removed for cosmetic reasons). A 2006 case study in the Dermatology Online Journal describes “the first report of supernumerary breast tissue on the foot.”

While in many cases, it’s a matter of one extra breast or nipple, there are instances of four, five, six or seven supernumerary breasts and/or nipples. In 1886, a doctor reported a woman with eight extra breasts — 10 in all. There was no word on how many children she nursed.

Interestingly, many women with polymastia are unaware of the condition until the tissue begins to respond to hormonal fluctuations brought on by menstruation, pregnancy or lactation, as the extra tissue gets bigger and more tender just like the normal breast.

“A patient will come in for acne and I’ll do a full body exam and notice it,” says Dr. Burdick. “When I ask them questions, it will turn out that it gets bigger with their period and is uncomfortable.”

Accessory breasts have also been known to lactate. One of the most famous cases in history is that of Therese Ventre of Marseilles, France, who had an extra breast on the outside of her left thigh. According to the 1827 report, the extra breast enlarged during puberty and produced milk when she became pregnant; a woodcut from the era shows her nursing children both at her breast and her thigh.

As is often the case with odd body phenomenon, men and women with supernumerary breasts and nipples were tortured and killed during the European witch hunts. Extra nipples were thought of as “witch’s teats,” used to nurse a familiar (a witch’s helper). Even Anne Boleyn, the unpopular second wife of Henry VIII, was said to have either an extra breast or extra nipple (along with an extra finger), although this may have just been bad press.

These days, polymastia and the more common polythelia are hardly considered a mark of the devil, but a stigma does remain for some, especially men.

“It can be very disturbing to a man to discover that he has accessory nipples, even more so, accessory breasts,” says Dr. Hema Sundaram, a Washington, D.C., dermatologist who has performed liposuction on accessory breast tissue with good results. “It can damage his feelings of masculinity and profoundly impact his self-esteem.”

Others, however, choose to celebrate their supernumerary self.

“I’ve come to embrace it,” Mark Wahlberg told Rolling Stone magazine in 2005 when asked about his third nipple. “That thing’s my prized possession.”