Accessory Breast Tissue |
| Accessory
breast tissue, also termed ectopic or supernumerary breast tissue,
refers to mammary tissue located anywhere on the body outside its
normal position on the anterior thoracic wall. It is a congenital
anomaly that originates during embryonic development. Around the sixth
week of gestation, paired mammary ridges, commonly called the "milk
lines," appear bilaterally on the ventral surface of the embryo and
extend from the axilla to the inguinal and vulvar region. Under normal
circumstances these ridges regress almost entirely, leaving only a
single pair of buds in the pectoral region that go on to form the adult
breasts. When regression fails or is incomplete at any point along this
line, residual mammary elements persist and may later develop into
accessory breast tissue. Because this represents the reappearance of a
structure typical of more primitive mammals, in which multiple paired
glands run the length of the trunk, the condition is regarded as
atavistic, a reversion to an ancestral pattern. Although the milk line
is the usual site, ectopic mammary elements have occasionally been
described well beyond it, including the neck, back, face, thigh, and
even the sole of the foot. The spectrum of accessory mammary tissue is conventionally described by a classification scheme dating from 1915 that divides it into eight categories according to which components, glandular tissue, nipple, and areola, are present. The most complete form contains all three elements and constitutes a fully formed supernumerary breast. Subsequent categories describe progressively incomplete combinations: glandular tissue with a nipple but no areola; glandular tissue with an areola but no nipple; glandular tissue alone, sometimes called mamma aberrata; a nipple and areola without underlying glandular tissue, known as pseudomamma; a nipple only, which is the classic supernumerary nipple or polythelia; an areola only, termed polythelia areolaris; and finally a patch of hair only, polythelia pilosa. In everyday practice two broad terms dominate: polythelia, denoting supernumerary nipples generally without associated breast tissue, and polymastia, denoting accessory glandular tissue with or without a nipple. The distinction is clinically meaningful because the presence or absence of true glandular tissue determines whether the lesion can undergo the same physiological and pathological changes as a normal breast. Reported prevalence varies considerably depending on the population studied and the definitions used, ranging broadly from about 0.22% to 6% of the general population. Polythelia tends to fall within the lower portion of that range, while accessory glandular tissue is reported in roughly 0.4% to 6% of women and 1% to 3% of men. Geographic and ethnic differences exist, with higher frequencies described among Asian and Japanese women and lower frequencies among those of Caucasian background. Supernumerary nipples have historically been described as somewhat more common in males, yet among patients who actually present for clinical evaluation or excision, the great majority are female and often young, likely because women more frequently seek correction for cosmetic or symptomatic reasons. Lesions are usually solitary and unilateral, though bilateral and multiple lesions occur; when unilateral, a slight predilection for the right side has traditionally been noted, although this is not invariable. By anatomical site, the axilla is by far the most common location for ectopic breast tissue, followed by other regions of the chest, the inframammary fold, and the abdomen. The condition is most often sporadic, but familial clustering is well recognized, including instances of male-to-male transmission. The proposed inheritance patterns are heterogeneous, encompassing autosomal dominant transmission with incomplete penetrance, X-linked dominant, and autosomal recessive modes, and somatic mutations arising early in embryonic life may also contribute. Accessory mammary tissue has been linked to congenital anomalies, most consistently of the renal and urinary tract, and less frequently to cardiovascular malformations, kidney tumors, and chromosomal conditions such as trisomy 21. These associations, however, are inconsistent, and large cohorts composed mainly of adults frequently identify no accompanying congenital anomaly at all. Because most congenital anomalies are detected in early childhood, the apparent rarity of associations in adult series may partly reflect the age at which patients present. Ultrasonographic screening of the kidneys and abdomen is sometimes recommended as part of diagnostic follow-up, particularly in younger patients. Clinically, accessory breast tissue is frequently asymptomatic and may be noticed only as a cosmetic concern or a cutaneous protuberance, often slightly more pigmented than surrounding skin. When functional glandular tissue is present, it responds to the same hormonal stimuli as orthotopic breast tissue, so the lesion may enlarge and become symptomatic at puberty, during pregnancy, or while breastfeeding. Forms consisting of glandular tissue alone, lacking an external nipple or areola, are especially prone to going unrecognized until hormonal stimulation makes them apparent. The characteristic complaint is a soft axillary mass, commonly a few centimeters in size, accompanied by cyclic pain coinciding with menstruation, swelling, tenderness, and fluctuation in volume. Larger lesions may restrict shoulder movement or cause irritation against clothing, and the cosmetic appearance often provokes anxiety. In children and adolescents the diagnosis is uncommon and may be delayed, yet it can occur even before menarche, and a tender, periodically enlarging axillary mass in this age group should raise suspicion. The differential diagnosis is broad and accounts for frequent misidentification. Accessory breast tissue has been mistaken for lipoma, lymphadenopathy, hidradenitis suppurativa, sebaceous cyst, vascular malformation, neurofibroma, lymphoma, and metastatic disease, among others. Ultrasonography is the preferred first-line imaging modality, demonstrating hypoechoic, septate, glandular-appearing tissue analogous to normal breast, sometimes with duct ectasia. Bilateral imaging is advisable to detect contralateral involvement, which may be asynchronous. Mammography and magnetic resonance imaging serve as useful adjuncts when the diagnosis is uncertain or when malignancy or another neoplastic process must be excluded, and fine-needle aspiration or core-needle biopsy can provide definitive confirmation. Histologically, the tissue shows the architecture of normal breast, with mammary lobules and lactiferous ducts in the dermis, surrounding connective tissue stroma, and bundles of nipple-type smooth muscle, often in proximity to cutaneous adnexal glands. Because it is genuine mammary tissue, the ectopic gland is susceptible to the full range of benign and malignant breast disease. Reported benign processes include fibroadenoma, fibrocystic change, ductal hyperplasia, duct ectasia, lactating adenoma, and intraductal or intracystic papilloma, the last being distinctly uncommon in this setting. Malignant transformation, while rare, is documented and includes ductal carcinoma in situ and invasive carcinoma. Importantly, tumors arise within glandular tissue rather than from a supernumerary nipple in isolation; when malignancy or significant proliferative disease is found in association with a supernumerary nipple, it typically reflects underlying accessory glandular tissue. This underscores the principle that wherever ectopic mammary tissue is identified, the possibility of accompanying breast pathology should be considered. Management is largely conservative. Surgical excision is reserved for symptomatic lesions, persistent cosmetic concern, diagnostic uncertainty, or suspicion of neoplasm, and prophylactic removal is not currently recommended. Excision through a small incision placed within a natural axillary fold is generally safe and effective, with liposuction reserved for larger lesions; reported complications include hematoma, seroma, infection, residual tissue, contour irregularity, and hypertrophic scarring. Operating before pregnancy is often favored because reoperation rates are lower and patient satisfaction higher. Overall, accessory breast tissue is a benign, usually innocuous condition whose chief clinical importance lies in correct recognition, distinction from other masses, and awareness of its capacity to develop the same diseases as a normally situated breast. References: 1- De la Torre M, Lorca-García C, de Tomás E, Berenguer B. Axillary ectopic breast tissue in the adolescent. Pediatr Surg Int. 38(10):1445-1451, 2022 2- El Malih S, Ezzahi M, Haloua M, Tahiri L, Akammar A, El Bouardi N, Alami B, Alaoui Lamrani MY, Maaroufi M, Boubbou M. Unusual intracystic papilloma arising from ectopic axillary breast tissue: Case report. Radiol Case Rep. 18(10):3414-3420, 2023 3- Class MM, McCoy K, Melin AA, Hafeez F, Abidi N, Krakowski AC. Bilateral accessory axillary breast tissue in a premenarchal female. Pediatr Dermatol. 41(4):704-706, 2024 4- Al Assaad M, Vulcain DR, Phan A, Boyraz B, Hoda SA. Polythelia (Supernumerary Nipple): Clinicopathological Characterization of an Atavistic Lesion. Int J Surg Pathol. 2025 33(8):1735-1741, 2025 5- Sag S, Sonmez Y, Gungormez EK, Canbaz FA, Gercel G, Yavuzer D, Yasar E, Thomas DT. Pediatric Breast Pathologies: 5-Year Experience and Proposal for a Risk-Based Management Algorithm. J Pediatr Adolesc Gynecol. S1083-3188(26)00309-8, 2026 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|