Are You Confident of the Diagnosis?
What you should be alert for in the history
The supernumerary nipple (SNN) is a common, minor congenital malformation that results in accessory nipples and/or mammary tissue. Most often, a SNN remains undetected and asymptomatic for long periods of time. It is sometimes noted by the patient during periods of hormonal change (puberty, menstruation, pregnancy) whereupon it can change in pigmentation, become tender, or even lactate.
Characteristic findings on physical examination
SNN in the neonate is easily overlooked during first examination. It can be a small, pearly or pigmented spot and may also be umbilicated or depressed. In older children and adults, the vast majority of SNNs are less than 30% the size of the normal nipple and the remaining are usually less than 50% the size of the normal appendage. Only rarely is the SNN the same size as the other two normal nipples (Figure 1, Figure 2).
95% of SNNs are found along the embryonic ’milk lines’ that extend from the axillary vaults, over the nipples, and down to the groin. The other 5% have been located ectopically on back, shoulder, extremities, face, neck, and genital areas. Usually there is a single SNN but in cases where there are mutliple SNNs present they can be distributed bilaterally or unilaterally, symmetrically or asymmetrically. It has been estimated that 13% of SNNs occur above the regular nipple. Study results are conflicting with regard to right-left side predominance.
Expected results of diagnostic studies
Dermascopic evaluation of the SNN reveals characteristics similar to a dermatofibroma. There are centrally located, white, scar-like areas surrounded by a fine pigment network. The SNN has a central cleft-like area that can help differentiate the two entities. Histopathologic evaluation is identical to a regular nipple. There is hyperpigmentation, mild hyperkeratosis, smooth muscle fascicles, pilosebaceous units, and, occasionally, mammary glands and ductal structures (Figure 3, Figure 4).
The differential diagnosis of SNN includes the following, all of which can be differentiated by histology:
Dermatofibroma (usually firm, displays the ’dimple’ sign)
Neurofibroma (displays the ’buttonhole’ sign)
Lymphangioma (often have vesicular, warty component)
Lipoma (no epidermal hyperpigmentation, subcutaneous)
Verruca (hyperkeratotic, thrombosed capillaries)
Who is at Risk for Developing this Disease?
The prevalence of SNN is thought to be approximately 1-2% but has been reported as high as 5.6%. The frequency of SNN also appears to vary between geographical area and ethnic groups. Many studies show a male predominance with an estimated 1.7:1 male:female ratio. While mostly sporadic, there have been familial cases reported.
What is the Cause of the Disease?
The vast majority of SNN occur along what are known as the mammary lines (aka Hughes lines, ’milk lines’). During weeks 4-5 of embryonic development two surface thickenings occur along each side of the embryo that extend from the axillary area to the groin. Later on in development of the ridges glandular elements are formed at the site of the future breasts while the others normally regress. When complete regression does not occur, SNN or any variant of breast tissue thereof can result.
Systemic Implications and Complications
The SNN has been reportedly associated with many other disease states and genetic syndromes. It has been most often associated with kidney and urinary tract malformations. This finding is controversial, however, and there have been numerous investigations that have both supported and refuted this claim. There is also a very small body of evidence linking the SNN to a variety of cardiac disorders including congenital heart anomalies, hypertension, and conduction defects.
Among the many other anecdotal associations of the SNN are carcinoma (renal, bladder, prostate, testicular), hematologic disorders, peptic ulcer disease, pyloric stenosis, skeletal malformations, central nervous system defects, accessory lung lobe, and laryngeal web.
The SNN has also been described in association with multiple genetic syndromes including Turner syndrome, Char syndrome (patent ductus arteriosus, hand abnormalities (most commonly a shortened or absent portion of the fifth digit) and distinctive facies), ectodermal dysplasia, Kaufman-McKusick syndrome (heart defects, polydactyly, and genital defects) and Fanconi anemia.
It is seen frequently in the Simpson-Golabi-Behmel syndrome which is categorized by macrosomia, mental retardation, distinct facies (macrocephaly, ocular hypertelorism, macrostomia, macroglossia, palatal abnormalities), variable GI, skeletal, renal, cardiac anomalies, and an increased incidence of tumorogenesis.
Treatment options are summarized in the Table I.
Optimal Therapeutic Approach for this Disease
Surgical excision is warrented if the patient desires removal for diagnostic or cosmetic reasons. Complete removal of the SNN and any associated mammary tissue may also be indicated if the patient is at increased risk of developing breast cancer.
If underlying breast tissue is present, the tumescent liposuction technique followed by simple excision of the nipple and/or excess skin has afforded the best cosmetic results. This procedure obviates the need for a wide local excision that can leave undesirable scarring.
There has been one reported case of successful treatment of bilateral SNNs with cryotherapy.
If the SNN is sporadic, explain to the patient and/or relatives that it is a common minor anomaly. There are no indications that further work-up is necessary in these cases. Be sure to stress that the lesion can potentially behave just as any ordinary nipple/breast tissue – it may undergo changes at puberty and lactate, develop mastitis, carcinoma, cysts, and Paget’s disease.
Prominent ectopic supernumerary nipples, familial lesions, and ones that are accompanied by other minor malformations should be worked up for associated kidney and urinary tract anomalies. Ultrasound imaging should suffice but other potential imaging studies include voiding cystography and intravenous pyelography. Keep in mind that these malformations can be silent. Nephrology and urology consultations may be prudent in these situations.
Unusual Clinical Scenarios to Consider in Patient Management
Remember that the SNN with accessory breast tissue can develop carcinoma. There have been a handful of reports of intraductal carcinoma arising within glandular tissue both immediately associated with and adjacent to the SNN. 60-70% of these lesions occur in the axillary region.
Be alert for any signs of a palpable mass, skin changes, nipple discharge, inversion, or retraction. Any of these symptoms require consultations for further investigation and imaging. Patients who are at high risk for breast cancer should be closely monitored and complete removal of the lesion and associated tissue should be considered.
There have also been rare cases of Paget’s disease arising in the SNN. Be alert for eczematous, sharply defined, infiltrated plaques on the skin of the SNN. There may be pruritus, pain, nipple discharge, or invagination. As mammary Paget’s disease is associated with underlying carcinoma, biopsy and imaging should be performed.
What is the Evidence?
Ferrara, P, Giorgio, V, Vitelli, O, Gatto, A, Romano, V, Del Bufalo, F. “Polythelia: Still a marker of urinary tract anomalies in children?”. Scand J Urol Nephrol. vol. 43. 2009. pp. 47-50. (A study of 166 children with KUTM and 182 controls that found a statistically significant increased incidence of SNN between the two groups (6.62% vs 1.09%). This is the most recent study addressing this controversial association.)
Grossi, NA. “Supernumerary breast tissue: Historical perspectives and clinical features”. South Med J. vol. 93. 2000. pp. 29-32. (A concise review of the basic clinical features of the SNN. Interesting historical anecdotes and prespectives.)
Schmidt, H. “Supernumerary nipples: prevalence, size, sex and side predilection – a prospective clinical study”. Eur J Pediatr. vol. 157. 1998. pp. 821-823. (A study with 502 subjects found a higher incidence than has been reported in the past. Found that 75% were ’small’ which was described as less than 30% diameter of the regular nipple. The finding of a male predominance corroborates other investigations but contradicted them in the finding of a increased left to right side ratio.)
Urbani, CE. “Supernumerary nipple and cardiocutaneous associations”. J Am Acad Derm. vol. 56. 2004. pp. e9(Short letter to the editor reviewing the reports of a potential link between the SNN and various cardiac anomalies.)
Fan, J. “Removal of accessory breasts: A novel tumescent liposuction approach”. Aesthetic Plast Surg. vol. 33. 2009. pp. 809-813. (A study of 47 women which reveals successful treatment and excellent cosmetic results with liposuction of ectopic breast tissue with or without SNN. The SNN and excess skin were excised immediately after the procedure. 43 of the 47 were satisfied with their final appearance. Good photographic evidence. Liposuction eliminates the need for large, unsightly scars resulting from wide local excision of these lesions.)
Rajaratnam, K, Kumar, PD, Sahasranum, KV. “Supernumerary nipple as a cutaneous marker of mitral valve prolapse in Asian Indians”. Am J Cardiol. vol. 86. 2000. pp. 695-897. (A small controlled study of 63 patients that found MVP more common in patients with SNN. Interesting finding but the authors admit that selection bias may have been a factor.)
James, A, Culver, K, Golabi, M, Pagon, RA, Bird, TC, Dolan, CR, Stephens, K. “Simpson-Golabi-Behmel Syndrome”. Gene Reviews (Internet). 1993-2006. (Concise description of this genetic syndrome focusing on medical genetics. Also addresses management and counseling issues.)
Kao, GF, Graham, JH, Helwig, EB. “Paget’s disease of the ectopic breast with an underlying intraductal carcinoma: report of a case”. J Cutan Pathol. vol. 13. 1986. pp. 59-66. (A good reminder for clinicians that the SNN can behave just as a regular nipple and is susceptible to the same pathologies. Nice review of both mammary and extramammary Paget’s disease.)
Sladden, MJ, Sladden, JA. “A novel treatment for accessory nipples”. Br J Dermatol. vol. 158. 2008. pp. 405(The authors describe a case where their patient’s primary care physician treated two SNNs with cryotherapy after diagnosing them as verruca. The lesions fell off with no complications.)
Youn, HJ, Jung, SH. “Accessory breast carcinoma”. Breast Care (Basel). vol. 4. 2009. pp. 104-106. (This is a nice case report and overview of breast carcinoma associated with SNN and ectopic breast tissue.)
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