chapter  2
Congenital disorders of the breast
ByEric Chang, David M. Kahn
Pages 7

The most common hyperplastic breast disorder is the supernumerary nipple, or polythelia. This is a relatively common occurrence, noted in 1-2 percent of the population ( 5 ). Incomplete regression of the embryonic mammary ridge tissues leads to the development of accessory nipples along the milk line. These can be found above the breast, in the axilla down to the level of the groin. Most commonly these are found in the inframammary area. Supranumerary nipples have been found in anatomic areas as varied as the scapula, head, neck, and thigh. Fifty percent of cases have been noted to be bilateral ( 6 ).