Supernumerary nipple (SNN) is a developmental abnormality that occurs most commonly over the anterior aspect of the trunk in the pathway of the embryonic milk lines. This report describes a histologic study of 48 cases with 51 SNN found among 360,000 consecutive skin biopsy specimens received in a dermatopathology laboratory. Histologically, the supernumerary nipple shows all the components observed in the nipple area, including eqidermal thickening, pilosebaceous structures, smooth muscles and mammary glands. A brief review of the literature is also made concerning the incidence and other characteristics of this lesion.