Sometimes referred to as accessory breasts, polymastia is the presence of supernumerary (extra) breasts on the human body. The extra breast tissue can appear in many forms, everything from a third nipple (the most common condition, referred to as polythelia) to a fully-formed, and fully-functional breast, in some unusual location on the body.

The linked article brings back memories of the chick from the movie Total Recall starring Governor Arnold Schwarzenegger...

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