Derm Dx: An embarrassing mole

Supernumerary nipples, also called accessory nipples, are fairly common, affecting between 1% and 6% of the general population. Men and women are equally affected, but supernumerary nipples are frequently more prominent and bothersome in women due to hormonal influences on...

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Supernumerary nipples, also called accessory nipples, are fairly common, affecting between 1% and 6% of the general population. Men and women are equally affected, but supernumerary nipples are frequently more prominent and bothersome in women due to hormonal influences on the accessory nipple tissue during puberty, pregnancy and menstruation. 

Supernumerary nipples are a form of accessory mammary tissue — breast tissue that occurs outside of the normally expected area of the chest. During embryonic development ectodermal thickenings, termed “mammary ridges” or “milk lines,” occur from the medial thigh to the anterior axilla. Breast tissue develops along this line.

In most instances, the milk line regresses and leaves only breast tissue in the pectoral area. However if the milk line fails to regress completely, breast tissue may persist outside of the pectoral area, leading to accessory mammary tissue. 

Supernumerary nipples may occur anywhere along the milk line; however, they are most commonly seen on the inframammary chest. Lesions are most frequently single, but multiple and bilateral accessory nipples are not uncommon. Typically, they appear as a small pink or brown soft papule. There may also be a surrounding areola. When the areola is present, the lesions may be termed pseudomamma. When absent, they are called polythelia. Occasionally, the areola develops without an associated nipple, which is referred to as polythelia areolaris. 

Sometimes ectopic glandular breast tissue develops either with or without an overlying supernumerary nipple. When the glandular breast tissue is present, patients may actually experience lactation through pores in the skin.

All accessory breast tissue is subject to the hormonal influences of puberty, pregnancy and menstruation. For example, it is not uncommon for women to complain of spontaneous tenderness of the accessory nipple during menstruation or for the nipple tissue to become more prominent during puberty. 

Diagnosis

The diagnosis is made clinically by a nipple or areola-like lesion, which has been present since birth and is located along the milk line. The clinical differential diagnosis includes melanocytic nevi (benign “moles” such as compound or intradermal nevi) or dermatofibroma. 

The histologic appearance of accessory nipple is the same as for a normal nipple. Key histologic features include the presence of smooth muscle, pilosebaceous units and glands. This is rather unique for nipple tissue and will rule out any other diagnosis. 

Treatment and prognosis

When desired, the treatment of choice is complete excision. As there is no clear association of supernumerary nipples with other developmental anomalies, imaging studies or other further workup is not indicated in the absence of other concerning clinical findings.

Adam Rees, MD, is a graduate of the University of California Los Angeles School of Medicine and a resident in the Department of Dermatology at Baylor College of Medicine in Houston.