Why Some People Have a Third Nipple

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The breasts develop early on in an embryo's development, typically during the fourth week of the gestation period. What are known as milk lines appear soon after, at around the sixth week of development. These arch down from the armpit to the groin on both sides of the body. As the breasts continue to develop, these lines eventually disintegrate, usually by about week nine. 

Occasionally, however, milk lines will persist and may be connected to extra breast tissue and extra nipples.

How Can Early Breast Development Lead To Extra Nipples?

In normal human development, the milk lines, for the most part, disappear. In some cases, however, there may be supernumerary breast tissue—extra nipples and breasts, also known as polythelia and polymastia, respectively—which can be an indication that the milk lines did not entirely disintegrate.

Extra nipples, if they are connected with the mammary glands, may be able to produce breast milk after pregnancy. Sometimes called accessory nipples or third nipples, they often look like moles or freckles and don't always have a connection with breast tissue or milk ducts.

Some Common Names for Extra Nipples

Beyond the terms polythelia, accessory nipple, and third nipple, you may hear the following:

  • Supernumerary nipple
  • Accessory nipple
  • Triple nipple
  • Vestigial nipple
  • Witch's nipple

Who Is Most Likely to Get an Extra Nipple?

Both men and women can develop an extra nipple. It is a fairly common abnormality that sometimes occurs in families but is more likely to develop at random.

Anne Boleyn, the wife of King Henry VIII of England, was said to have had a third nipple. Scaramanga, an infamous Bond villain, had an accessory nipple and this was what made him easy to identify. Scientists named the Scaramanga gene after him; it is this gene that produces a protein called Neuregulin-3 (NRG3), which provides a signal to embryonic cells telling them to become breast cells.

Accessory Nipples, Breast Cancer, and Other Conditions

If you have one or more extra nipples, you may wonder if this increases your risk for breast cancer. Any breast tissue you have, whether it appears in the standard location or elsewhere, is vulnerable to the same diseases that can affect typical breast tissue.

The presence of extra nipples is sometimes also linked to heart defects and kidney disease. Paget's disease of the nipple can sometimes show up in your groin area (lower end of the milk lines) where it is called extramammary Paget's disease (EMPD).

How Do I Care for My Extra Nipples?

In most people, extra nipples are benign and may never be noticed. But if you know that you have an extra nipple, do see your doctor if it changes, has discharge, or develops a lump or rash. If you have an extra nipple and it bothers you, it can be surgically removed, just like a mole.

Milk lines, also known by the technical term ventral epidermal ridges, are precursors to the mammary glands and nipples.

Not all nipple changes indicate breast cancer, but knowing which are expected changes and which are signs of disease is critical to your breast health.

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Article Sources
  • Dermoscopic features of accessory nipples. Murat Orhan Oztas, MD, and Mehmet Ali Gurer, MD. International Journal of Dermatology, Volume 46 Issue 10, Pages 1067 - 1068. Published Online: 1 Oct 2007.
  • Familial polythelia over three generations with polymastia in the youngest girl. Galli-Tsinopoulou A; Krohn C; Schmidt H. Eur J Pediatr. 2001 Jun;160(6):375-7.
  • The role of NRG3 in mammary development. Beatrice A Howard. J Mammary Gland Biol Neoplasia. 2008 Jun;13(2):195-203. Epub 2008 Apr 17.
  • Variations in Development. Variations Apparent at Birth; Pp. 51- 53. Dr. Susan Love's Breast Book. Susan M. Love, M.D. Third Edition, 2000.