Also in this week's column:
- Is it true that a woman's breasts can grow enormously overnight?
- Why is it absolutely impossible to sneeze with your eyes open?
- Why do we open our mouths to yawn properly?
Why do some people have three nipples?
Asked by Kumari Issar of Mumbai, India
It is not widely known, but about one in 50 women and one in 100 men have a third nipple. This goes by several names besides “third nipple”. It is a supernumerary nipple, accessory nipple, pseudomamma, polythelia, or polymastia. It is often not entirely developed as a fully functioning nipple. Sometimes it can be mistaken for a mole. The third nipple usually has no clinical significance as long as nothing else is wrong.
All mammals can develop an extra nipple. Nipple development is classified into eight levels. The first level is the mole-like nipple. The eighth level is a fully developed, female, milk-bearing breast in a female and a fully developed, male, non-milk bearing breast in a male. “Supernumerary” and “accessory” both mean extra. Pseudomamma refers to false or unnecessary breast tissue generally. Polythelia refers to the appearance of the additional nipple alone.
Polymastia refers to the appearance of the additional nipple along with the presence of mammary glands. The third nipple is merely one of those anomalies that arise in human populations. Call it a birth defect if you will, but it is not a very important one. The third nipple usually forms along the two vertical “milk lines” which start from the armpit, run down through the breasts, and further down to the groin in both women and men.
A team from the Breakthrough Breast Cancer Research Centre in London has recently discovered the gene that makes the growth factor that triggers breast and nipple growth. The team of researchers, headed by Dr. Alan Ashworth, has named the gene, the Scaramanga gene, after the three-nippled villain in the James Bond film, “The Man With The Golden Gun” (played by Christopher Lee). The discovery allows researchers to move one step closer to growing breast tissue in the laboratory and thus better study breast cancer and other breast tissues diseases. See Genes and Development (September, 2005).
A third nipple usually occurs somewhere on the chest, but not always. Brazilian researchers recently reported the first case of a nipple occurring on (wait for it) the bottom of the foot. The case is that of a 22-year-old woman. Her foot nipple was fairly well developed with “well-formed nipple surrounded by areola and hair”. Dr. D.M. Conde and three colleagues from the Department of Gynecology and Obstetrics at the Hospital Estadual Sumare and the Universidade Estadual de Campinas in Sumara reported the case in May 2006 in Dermatology Online Journal.
Stephen Juan, Ph.D. is an anthropologist at the University of Sydney.
Liked this article? You can check out all The Odd Body columns here.