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1.
Accessory breasts, also known as polymastia, supernumerary breasts, or mammae erraticae, is the condition of having an additional breast. Extra breasts may appear with or without nipples or areolae.

A related condition, in which extra nipples form, is called "supernumerary nipple" or "polythelia".

Your mother has polymastia.
by chris timmons February 15, 2008