Extra (supernumerary or accessory) nipples or breast tissue

Extra nipples or breast tissue is fairly common (1-6% of women) and is a result of incomplete regression of the mammary ridge (milk line) during the development of the embryo before birth.

What Does Having a Third Nipple Mean? Supernumerary Nipples - GoodRx

Figure 1 from Supernumerary breast in an adolescent boy.

Oh! The places you can Grow! Accessory Breast Tissue — Mattos Lactation

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Supernumerary nipple and seminoma: Case report and review of polythelia and genitourinary cancers

If a girl has a third nipple, would it develop into a third breast

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lactation-physiology

स्तनपान के दौरान स्तनों में दर्द

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Accessory Nipple Removal: Cost, Reviews, Safety

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Report: Woman Gets Third Breast in Bid for Reality TV Show

I lied about my accident as a teen — now I'm a mom of two with a weird third boob