Multiple Nipples and Extra Breasts
A supernumerary nipple is the aborted beginning of an additional nipple along Hughes lines, also known as mammary lines or simply milk lines extending from the axilla to the pubic region. The hyperpigmented macule may have features more or less descriptive of a fully formed nipple, and occur a couple centimeters below the usually placed nipple. They are most often singular, and unilateral.
The presence of extra nipples and breasts, polythelia and polymastia respectively, is not uncommon. It was once thought that this condition was a symbol of increased fertility and femininity. It was once also considered the witch’s mark. Polymastia (supernumerary breasts) and polythelia (supernumerary nipples) are extras in sites unexpected. These anomalies appear more so in women than men. The full spectrum of extra parts - from nipples to fully formed breasts - is wide-ranging.
The genesis of extra breasts lies in hidden, quiescent primordial breast tissue along the milk lines. In the fourth to fifth weeks of normal embryonic development, two surface thickenings occur along the sides of the embryo. In 2 to 3 months, these thickenings become more pronounced as mammary ridges - the future site of breasts. Normally most of these ridges (all except two) regress. But as imperceptibly as the germination of a dormant seed in early spring soil, such ectopic quiet breast rudiments can come to life in the right hormonal milieu, when awash in sex hormones at puberty or during pregnancy.