A supernumerary nipple (also known as a third nipple, accessory nipple, polythelia or polymastia) is an additional nipple occurring in mammals including humans. Often mistaken for moles, supernumerary nipples are diagnosed at a rate of 2% in females, less in males. The nipples appear along the two vertical "milk lines" which start in the armpit on each side, run down through the typical nipples and end at the groin. They are classified into eight levels of completeness from a simple patch of hair to a milk-bearing breast in miniature. Polythelia refers to the nipple alone while polymastia denotes the presence of glandular tissue.
In Popular Culture
Actor and singer Mark Wahlberg is seen to have such a nipple below his left breast in his modelling photographs.
Fictional characters said to have 'a third nipple' include:
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