Wo m e n ’s I m a g i n g • R ev i ew DeFilippis and Arleo Accessory Breast Tissue
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Women’s Imaging Review
The ABCs of Accessory Breast Tissue: Basic Information Every Radiologist Should Know Ersilia M. DeFilippis1 Elizabeth Kagan Arleo DeFilippis EM, Arleo EK
OBJECTIVE. Accessory breast tissue, residual breast tissue persisting from embryologic development, is found in up to 6% of the population, most commonly in the axilla along the “milk line.” CONCLUSION. Radiologists should be able to recognize the imaging appearance of this normal variant on multiple modalities, while at the same time understanding that the same spectrum of pathologic processes that occur in normal breast tissue can occur in accessory breast tissue as well.
A
Keywords: aberrant breast tissue, accessory breast tissue, ectopic breast tissue, milk line, supernumerary breasts DOI:10.2214/AJR.13.10930 Received March 20, 2013; accepted after revision August 23, 2013. 1 Both authors: New York-Presbyterian Hospital/Weill Cornell Medical Center, 425 E 61st St, 9th Fl, New York, NY 10065. Address correspondence to E. K. Arleo ([email protected]).
AJR 2014; 202:1157–1162 0361–803X/14/2025–1157 © American Roentgen Ray Society
ccessory breast tissue is defined as “residual [breast] tissue that persists from normal embryologic development” [1]. Also known as ectopic breast tissue, accessory breast tissue can be found in up to 6% of the population [2]. The highest incidence occurs in the Japanese population [3], with the lowest incidence in white individuals [4]. More specifically, ectopic breast tissue is an umbrella term that refers to both supernumerary breasts as well as aberrant breast tissue [3, 5]. Supernumerary breasts are often found anywhere along the “milk line,” an embryologic landmark that runs bilaterally from the anterior axillary folds to the inguinal region and medial thigh [6]. The term “aberrant breast tissue” is defined as “an island of breast tissue usually located in proximity to the normal breast” [4]. Aberrant breasts consist of accessory fragments of breast tissue outside the periphery of the gland [5]. In contrast to supernumerary breasts, aberrant breast tissue lacks organized secretory systems [4]. For the purposes of this article, the term “accessory breast tissue” will be used for consistency. Accessory breast tissue is most commonly located in the axilla, but locations outside the milk line, including the face, posterior neck, chest, middle back, buttock, vulva, flank, hip, shoulder, upper extremities, and posterior and lateral thigh have also been reported [7]. There may be an autosomal-dominant inheritance pattern with incomplete penetrance, but most cases are sporadic [7]. Regardless of the location of the accessory
breast tissue, a patient with accessory breast tissue may be asymptomatic and unaware of the presence of accessory breast tissue. Alternatively, because accessory breast tissue, like normal breast, responds to hormonal influences, it may come to attention during menarche, pregnancy, or lactation [2, 8]. Knowledge about accessory breast tissue has important implications for patient care: If accessory breast tissue is not recognized for what it is, then a normal variant may be misdiagnosed as an abnormality. The most common presumptive diagnoses reported in the literature include lipoma, lymphadenopathy, sebaceous cyst, vascular malformation, and malignancy [9]. At the same time, it is important to recognize that the same spectrum of pathologic processes that occur in normal breast tissue can occur in accessory breast tissue, including benign processes such as fibrocystic changes, mastitis, and fibroepithelial lesions; atypical ductal or lobular hyperplasia; and frank malignancy [2]. If surgical treatment is required, then this raises the questions of the appropriate operative and postoperative management of accessory breast tissue. Given these issues, the objective of this article is to provide a focused, comprehensive, in-depth discussion of the available scientific information on accessory breast tissue. Embryology In the fourth week of human development, a pair of mammary ridges derived from ectoderm form [10]. These ridges, often referred to as the “milk line,” run bilaterally along the
AJR:202, May 2014 1157
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DeFilippis and Arleo ventral surface of the body from the anterior axillary folds to the medial aspect up the inguinal folds. Normally, these ridges regress except at the site of the breasts [10]. This embryology informs the embryologic theory of accessory breast tissue—namely, that it represents the failure of regression or displacement of the milk line [11–15]. However, this theory fails to account for reported cases of accessory breast tissue outside the milk line, leading to other proposed explanations. In 1950, Hughes [16] proposed that independently migrating nests of primordial breast cells can develop in a completely random manner. Later, Craigmyle [17] alternatively suggested that accessory breast tissue develops from modified apocrine sweat glands. Accessory breast tissue can contain all elements present in normal breast tissue—parenchyma, areola, and nipple [2]. In 1915, a classification system for supernumerary breast tissue, authored by Kajava [18], was published [3, 9]. Class 1 is termed “polymastia” and consists of a complete breast with a nipple, areola, and glandular tissue. Class 2 is a supernumerary breast without an areola, consisting of glandular tissue and a nipple. Class 3 consists of an areola and glandular tissue. Class 4 is glandular tissue only. Class 5 contains a nipple and areola only and is termed “pseudomamma.” Class 6 consists of just a nipple (polythelia), and class 7 consists of just an areola (“polythelia areolaris”). Last, class 8 is termed “polythelial pilosis” and consists of just a patch of hair. Thus, the most common clinical manifestation of accessory breast tissue, fibroglandular tissue in the axilla, is class 4. One or more supernumerary nipples (polythelia) or supernumerary breasts (polymastia) can form along the mammary ridges, and both can enlarge and lactate in response to hormones [10]. Accessory breast tissue is sometimes associated with congenital anomalies of the urogenital system. Estimates of renal anomalies and urologic anomalies in patients with supernumerary nipples range from 11% to 27% [8]. Specifically, accessory nipples can be associated with supernumerary kidneys, failure of renal formation, and renal cell carcinomas [19]. Normal Appearance of Accessory Breast Tissue It is important to recognize the appearance of accessory breast tissue on imaging so that it can be appropriately diagnosed as a normal variant and not a pathologic ab-
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normality. History and physical examination findings suggestive of accessory breast tissue include masses associated with pain or discomfort, milk secretion, and local skin erythema that may be more prominent during pregnancy and lactation [1, 3]. Accessory breast tissue is frequently bilateral, so clinical suspicion should prompt physical examination of the relevant contralateral region [3]. Laboratory analyses add little to no value. Depending on the patient’s age and clinical presentation, imaging evaluation might begin with mammography or ultrasound; alternatively, mammography or ultrasound performed for routine screening or diagnostic purposes might show accessory breast tissue incidentally. Diagnostic breast MRI is occasionally performed in challenging atypical cases or may note accessory breast tissue as an incidental finding. Definitive diagnosis can be established by fine-needle aspiration or excisional biopsy; however, knowledge of the normal appearance of accessory breast tissue on multiple modalities should hopefully preclude such unnecessary invasive procedures [20]. Mammography Figure 1 shows the normal mammographic appearance of accessory breast tissue in the axilla. There may be a small to large amount of fibroglandular elements and densities interspersed with fat that radiographically have the same appearance as normal glandular parenchyma but are located separate from the main breast parenchyma [21]. In contradistinction to the relatively frequent sighting of the axillary tail of Spence, which is a continuous extension of the tissue of the breast that extends into the axilla, accessory breast tissue in the axilla is discontinuous with the main breast parenchyma [21]. However, it should be specifically mentioned that an axillary focal asymmetry on a baseline examination should not automatically be assumed to represent accessory breast tissue. Although this may ultimately be the conclusion, as illustrated in Figure 1, if an axillary focal asymmetry is seen on baseline examination (Fig. 1A), then the patient should be recalled for additional imaging evaluation (Fig. 1B) to prove the hypothesis and exclude other causes (Fig. 2). If an axillary focal asymmetry that represents a change from previous studies is seen, then this finding is especially concerning for a developing malignancy.
Ultrasound Ultrasound is usually the first-choice imaging modality for evaluation of any palpable soft-tissue mass outside the breast and may be the imaging modality of initial choice for a palpable breast mass if the patient is younger than 30 years old [22]. With real-time gray-scale and color Doppler imaging, and without ionizing radiation, sonography can be used to help differentiate a mass of accessory breast tissue from, particularly in the axilla, lipomas, lymphadenopathy, and other pathologic entities [23]. Figure 2 shows the normal sonographic appearance of accessory breast tissue in the axilla. The appearance of accessory breast tissue on ultrasound, irrespective of location, is the same as the appearance of breast tissue within the breast: Fibroductal tissue and lobules of fat are visualized. MRI On MRI, accessory breast tissue can appear as a subcutaneous ill-defined mass or nonmasslike area that has signal intensity and contrast enhancement similar to the rest of the breast parenchyma but is discontinuous with that tissue [9]. Figure 3 shows the normal appearance of accessory breast tissue on MRI. As seen on other modalities as well, the amount of accessory breast tissue within an axilla might be small, moderate, or large; the accessory breast tissue may be symmetric or asymmetric, and its enhancement might be minimal, mild, moderate, or marked similar to the enhancement of the rest of the background parenchyma. In the literature, MRI has been reported to be a useful modality for the diagnosis of ectopic breast tissue in peripubertal or pubertal girls presenting with an axillary mass of uncertain cause [1]. Pathologic Findings in Accessory Breast Tissue Benign All diseases of the breast also occur in accessory breast tissue. Figure 4 illustrates the case of a 37-year-old woman from our institution, 10 days postpartum, who presented with a palpable area of concern in the right axilla that had decreased in size somewhat since delivery. Her medical history was significant for bilateral mastectomies approximately 1.5 years earlier for invasive and in situ ductal carcinoma on the right (which presented as calcifications on mammography) and atypical lobular hyperplasia on the left, followed by bilateral implant reconstruction; genetic testing
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Accessory Breast Tissue was negative. Ultrasound of the right axilla in the palpable area of concern showed a 2.5-cm oval circumscribed mass parallel to the skin with echogenic septations, an echogenic pseudocapsule, and mild internal vascularity. Because of the presence of a new palpable mass in this high-risk patient, ultrasound-guided core biopsy of the right axillary mass was recommended and performed; pathology yielded lactating adenoma, thus supporting the presence of residual axillary accessory breast tissue postmastectomy. Surgical excision was considered, but the patient declined; at clinical follow-up 6 months later, the palpable area of concern had regressed, supporting the pathologic diagnosis of lactating adenoma, the prognosis of which is regression after completion of breast feeding [24]. Cases of other benign pathologic entities occurring in accessory breast tissue have been reported in the literature. For example, several case reports exist of fibroadenomas in accessory breast tissue, including one in a 17-year-old girl who presented with a mobile, firm, and painless mass in the left axilla that gradually increased in size over the course of 3 years. Ultrasound showed a well-circumscribed, homogeneous solid mass that at pathology was a fibroadenoma similar to that seen in normal breast tissue [19]. On gadolinium-enhanced MRI, enhancement of the fibroadenoma in accessory breast tissue can be variable depending on the degree of fibrosis in the tumor [23]. Mammary hamartomas have also been reported to occur in accessory breast tissue. For example, one case report describes a 38-year-old woman with a hamartoma in an accessory breast [23]. Mammography of the accessory breast showed “a circumscribed mass that consists of both soft-tissue and lipomatous elements surrounded by a thin radiolucent zone” and accompanying ultrasound showed an “elongated well-circumscribed mixed echoic mass originating from accessory breast tissue” [23]. Fat necrosis, a benign nonsuppurative inflammatory process of adipose tissue that can occur in response to trauma, has also been reported to occur in accessory breast tissue. One case in the literature describes a 32-year-old woman who underwent chest radiography, which showed indeterminate calcifications in the right axilla for which further imaging was recommended [23]. Sonography showed “poorly defined hypoechoic lesions,” with “curvilinear echogenic foci with posterior shadowing within the mass,”
compatible, in conjunction with the radiographic findings, with fat necrosis [23]. Fat necrosis, hamartomas, fibroadenomas, and lactating adenomas are just four examples of benign pathologic entities that can occur in accessory breast tissue. Malignant There is controversy in the literature as to whether there is an increased risk of malignant transformation in accessory breast tissue compared with pectoral breast tissue. Some studies have suggested an increased incidence of cancer in aberrant breast tissue [4], whereas others suggest that there is no evidence to support this [5]. Investigators have hypothesized that stagnation arising in the lumina of ducts of aberrant breast tissue may play a role in the development of malignancy [4]. In one study, 94% of ectopic breast cancers arose from aberrant tissue as opposed to 6% in supernumerary breasts [4]. Interestingly, the incidence of accessory breast tissue cancer in males has also been reported to be higher than that of pectoral male breast cancer [25]. Cancer in ectopic breasts, stage-for-stage, appears to arise at an earlier age than the same disease in pectoral developmentally normal breast tissue [4]. For example, in one review of 82 cases of ectopic breast cancer in 81 patients, the mean age at diagnosis was 53.3 years (median, 54 years), an average age lower than the average age for pectoral breast cancer [4]; according to statistics from the National Cancer Institute, the median age at diagnosis for breast cancer is 61 years [26]. Furthermore, patients presented with more extensive disease, probably secondary to a delayed diagnosis and less likely because of the disease process itself; however, the possibility that malignancy that exists near the axillary lymph nodes may metastasize earlier than carcinoma of the normal breast has been raised [4, 5, 27]. The most frequently reported malignant disease in ectopic breast tissue is infiltrating ductal carcinoma (79%) [3]. Rare reports of Paget disease, cystosarcoma phyllodes, papillary carcinoma, leiomyosarcoma, and invasive secretory carcinoma also exist [3]. Accessory mammary carcinoma is thought to account for 0.3–0.6% of all breast cancer cases, usually manifesting as an axillary mass [25]. One such example from our institution is shown in Figure 5. Other presentations include suspicious microcalcifications in axillary tissue, as shown in Figure 6. Ac-
cessory breast tissue carcinoma may be asymptomatic and picked up on routine screening, as was the case in both patients shown in Figures 5 and 6, or may be symptomatic, with symptoms similar to carcinoma of the pectoral breast, and be referred to diagnostic mammography. The most common sign seen on physical examination is a palpable lump, but edema and tenderness can also be noted [7]. Interestingly, in the case of the 50-yearold woman in Figure 6, the patient had a long history of bilateral axillary fat pad tissue that has been atypically tender in relation to her menstrual cycles and the presumed diagnosis of bilateral axillary breast tissue had been made in the past. If a mass can be seen sonographically within accessory breast tissue, then tissue sampling can be achieved by ultrasound-guided core biopsy. If accessory breast tissue calcifications are the only imaging finding, then stereotactic core biopsy may be attempted if the calcifications appear amenable. However, if the calcifications are located in accessory breast tissue in the axilla near the chest wall, then they may be difficult to target by this method and if not seen sonographically, surgical excision or lumpectomy may be pursued. The pathology literature reports that it can sometimes be difficult to differentiate breast carcinoma in axillary accessory breast tissue from adenocarcinoma of the sweat glands in the axilla, but identification of estrogen and progesterone receptors can be helpful. Under the microscope, visualization of aberrant normal breast tissue adjacent to an axillary tumor is also used to differentiate primary carcinoma in accessory breast tissue from metastatic cancer to the axilla from an unknown primary site [25, 27]. Cancer of accessory breast tissue can also occur concurrently with cancer in a pectoral breast [4, 28]. In 1976, the first such case was described of a woman who developed primary carcinoma in both breasts as well as in ectopic breast tissue in her vulva [28]. In 1994, Marshall et al. [4] described the case of a woman with lobular carcinoma in a supernumerary breast and infiltrating ductal carcinoma in her left breast. Accessory Breast Tissue Management Most patients with accessory breast tissue are unaware of the presence of accessory breast tissue and are asymptomatic. Thus, although no treatment is required in most cases of accessory breast tissue, in asymptomatic patients who are being screened for breast
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DeFilippis and Arleo cancer or diagnostic patients with a personal history of breast cancer undergoing routine surveillance, the possibility of disease in accessory breast tissue should be considered. The case of the lactating adenoma at our institution proves that this postmastectomy patient had residual axillary accessory breast tissue given that a specific, albeit benign, abnormality arose in that location. It raises questions regarding whether patients with bilateral mastectomies should undergo annual surveillance of the axillae if accessory breast tissue is known and whether preoperative mammography or other breast imaging should definitively comment on the presence or absence of accessory breast tissue to guide the surgeon for a possible wider excision. The treatment of choice for symptomatic accessory axillary breast tissue is surgical excision because removal of the tissue will relieve physical discomfort in the case of a large volume of accessory tissue. Accessory breast tissue may also be removed for cosmetic reasons. In the axilla, accessory breasts can be satisfactorily treated with excision, liposuction, or both [29, 30]. Management of accessory breast tissue cancer should follow the recommendations set forth for pectoral breast cancer of parallel TNM classification [4]. Given the variety of locations of ectopic breast cancers, it is important to understand the lymphatic drainage of the malignant site [4]. Some authors recommend radical mastectomy of the ipsilateral breast, whereas others report that ipsilateral mastectomy does not improve prognosis for ectopic breast carcinoma [7]. Although it might be a concern that patients with an ectopic cancer have an increased risk for developing a second primary cancer, this risk is not considered to be enough to justify prophylactic ipsilateral mastectomy [4]. Others propose that the surgical procedure of choice in the treatment of ectopic breast carcinoma includes wide resection of the tumor with the surrounding tissue, covering skin, and regional lymph nodes [4]. Postoperative treatment of accessory breast tissue is the same as for anatomic breast carcinoma. Estrogen receptor, progesterone receptor, and HER2/neu testing should be performed on accessory breast tissue cancers as is done for pectoral breast cancers [31, 32]. Radiation of the accessory breast tissue tumor site is regularly performed [7], and adjuvant chemotherapeutic and hormonal therapy options should be carried out in accordance with the recommendations for pectoral breast cancers [31].
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Conclusions With accessory breast tissue occurring in up to 6% of the population, most commonly in the axilla but potentially anywhere along the milk line, radiologists should be familiar with its normal appearance on multiple modalities. The clinical significance of accessory breast tissue is that it needs to be recognized for what it is or a normal variant may be misdiagnosed as an abnormality. At the same time, it is important for the radiologist to keep in mind that all diseases of the breast can also occur in accessory breast tissue, including both benign and malignant ones, as this article has illustrated. References 1. Laor T, Collins MH, Emery KH, Donnelly LF, Bove KE, Ballard ET. MRI appearance of accessory breast tissue: a diagnostic consideration for an axillary mass in a peripubertal or pubertal girl. AJR 2004; 183:1779–1781 2. Goyal S, Puri T, Gupta R, Julka P, Rath G. Accessory breast tissue in axilla masquerading as breast cancer recurrence. J Cancer Res Ther 2008; 4:95–96 3. Bakker JR, Sataloff DM, Haupt HM. Breast cancer presenting in aberrant axillary breast tissue. Commun Oncol 2005; 2:117–120 4. Marshall MB, Moynihan JJ, Frost A, Evans SR. Ectopic breast cancer: case report and literature review. Surg Oncol 1994; 3:295–304 5. Rho JY, Juhng SK, Yoon KJ. Carcinoma originating from aberrant breast tissue of the right upper anterior chest wall: a case report. J Korean Med Sci 2001; 16:519–521 6. Hong JH, Oh M-J, Hur J-Y, Lee JK. Accessory breast tissue presenting as a vulvar mass in an adolescent girl. Arch Gynecol Obstet 2009; 280:317–320 7. Youn HJ, Jung SH. Accessory breast carcinoma. Breast Care (Basel) 2009; 4:104–106 8. Velanovich V. Ectopic breast tissue, supernumerary breasts, and supernumerary nipples. South Med J 1995; 88:903–906 9. Sahu SK, Husain M, Sachan PK. Bilateral accessory breast. The Internet Journal of Surgery. www.ispub.com/journal/the-internet-journal-ofsurgery/volume-17-number-2/bilateral-accessorybreast.html#sthash.VP7wyAQQ.dpbs. Published 2008. Accessed February 10, 2013 10. Schoenwolf GC, Bleyl SB, Brauer PR, Francis-West PH. Development of the skin and its derivatives. In: Larsen WJ, ed. Human embryology, 4th ed. Philadelphia, PA: Churchill Livingstone, 2009:193–216 11. de Cholnoky T. Supernumerary breast. Arch Surg 1939; 39:926–941 12. Hamilton WJ, Boyd JD, Mossman HW. Human embryology. Baltimore, MD: Williams & Wilkins, 1945 13. Haagensen CD. Diseases of the breast, 2nd ed. Philadelphia, PA: Saunders, 1971
14. Schultz A. Pathologische anatomie der brusdruse: handbuch der speziellen. In: Henkee F, Lubarsch O, eds. Pathologischen anatomie and histologie, vol. VII. Berlin, Germany: Springer-Verlag, 1933 15. Hanson E, Segóvia J. Dorsal supernumerary breast: case report. Plast Reconstr Surg 1978; 61:441–445 16. Hughes ES. The development of the mammary gland: Arris and Gale Lecture, delivered at the Royal College of Surgeons of England on 25th October, 1949. Ann R Coll Surg Engl 1950; 6:99–119 17. Craigmyle MB. The apocrine glands and the breast. New York, NY: Wiley, 1984:49–55 18. Kajava Y. The proportions of supernumerary nipples in the Finnish population. Duodecim 1915; 31:143–170 19. Mukhopadhyay M, Saha AK, Sarkar A. Fibroadenoma of the ectopic breast of the axilla. Indian J Surg 2010; 72:143–145 20. Farcy DA, Rabinowitz D, Frank M. Ectopic glandular breast tissue in a lactating young woman. J Emerg Med 2011; 41:627–629 21. Adler DD, Rebner M, Pennes DR. Accessory breast tissue in the axilla: mammographic appearance. Radiology 1987; 163:709–711 22. American College of Radiology website. ACR Appropriateness Criteria for palpable breast masses. www.acr.org/~/media/ACR/Documents/AppCriteria/Diagnostic/PalpableBreastMasses.pdf. Published 1996. Updated 2012. Accessed June 27, 2013 23. Kim EY, Ko EY, Han BK, et al. Sonography of axillary masses: what should be considered other than the lymph nodes? J Ultrasound Med 2009; 28:923–939 24. Dähnert W. Radiology review manual, 6th ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2011 25. Yamamura J, Masuda N, Kodama Y, et al. Male breast cancer originating in an accessory mammary gland in the axilla: a case report. Case Report Med 2012; 2012:286210 26. National Cancer Institute website. SEER stat fact sheets: breast. seer.cancer.gov/statfacts/html/breast. html. Accessed June 26, 2013 27. Cogswell HD, Czerny EW. Carcinoma of aberrant breast of the axilla. Am J Surg 1961; 27:388–390 28. Guerry RL, Pratt-Thomas HR. Carcinoma of supernumerary breast of vulva with bilateral mammary cancer. Cancer 1976; 38:2570–2574 29. Aydogan F, Baghaki S, Celik V, et al. Surgical treatment of axillary accessory breasts. Am Surg 2010; 76:270–272 30. Fan J. Removal of accessory breasts: a novel tumescent liposuction approach. Aesthetic Plast Surg 2009; 33:809–813 31. Gutermuth J, Audring H, Voit C, Haas N. Primary carcinoma of ectopic axillary breast tissue. J Eur Acad Dermatol Venereol 2006; 20:217–221 32. Madej B, Balak B, Winkler I, Burdan F. Cancer of the accessory breast: a case report. Adv Med Sci 2009; 54:308–310
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Fig. 1—Normal appearance of accessory breast Breast Accessory tissue on mammography. A, 37-year-old asymptomatic woman presented for baseline screening mammography. Asymmetry (circle) is seen on right, upper hemisphere, posterior plane on mediolateral oblique view. B, Patient was recalled for finding shown in A. Mammogram shows patch of pliable fibroglandular tissue with interspersed fat discontinuous with majority of breast tissue more inferiorly, which is consistent with accessory breast tissue, and benignappearing axillary lymph nodes. To confirm these findings, ultrasound was performed (Fig. 2).
A
Fig. 2—Normal appearance of accessory breast tissue on ultrasound of 37-yearold asymptomatic woman (same patient as Fig. 1). Gray-scale image targeted to right axilla shows original mammographic area of concern. Arrow indicates dermis, half bracket indicates retromammary layer, and bracket indicates accessory breast tissue between dermis and retromammary layer.
Tissue
B
Fig. 3—Axial image from contrast-enhanced (12 mL of gadolinium) VIBRANT (Volume Image Breast Assessment, General Electric Company) fast 3D gradientecho sequence with T1-weighting and fat suppression (TR/TE, 5.76/2.752; flip angle, 10°) of 41-year-old woman shows normal appearance of accessory breast tissue (bracket). Small to moderate amount of accessory breast tissue is seen in left axilla with mild enhancement.
Fig. 4—37-year-old woman with bilateral mastectomies (for invasive and in situ ductal carcinoma on right and atypical lobular hyperplasia on left) who presented for surveillance imaging was found to have lactating adenoma in residual axillary accessory breast tissue. Gray-scale image of right axilla shows 2.5-cm palpable, oval, circumscribed mass parallel to skin with echogenic septations, echogenic pseudocapsule, and mild internal vascularity. Ultrasound-guided core biopsy was performed, with pathology yielding lactating adenoma.
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DeFilippis and Arleo
A
B
C
Fig. 5—88-year-old woman with infiltrating and in situ lobular carcinoma in axillary accessory breast tissue presenting as mass. A, Bilateral mediolateral oblique (MLO) images from screening mammography show asymmetry in left axillary breast tissue (circle). B, Spot compression view of left axilla in MLO projection shows high-density irregular mass with spiculated margins. C, Ultrasound image of left axilla targeted to mammographic abnormality shows 9-mm hypoechoic irregular mass with spiculated margins (cursors); core biopsy was performed, with pathology yielding infiltrating and in situ lobular carcinoma (low nuclear grade).
Fig. 6—50-year-old woman with ductal carcinoma in situ (DCIS) in axillary accessory breast tissue presenting as microcalcifications. Screening mammogram (not shown) showed faint microcalcifications in accessory breast tissue in right axilla, and patient was recalled for additional imaging. Spot magnification view of right axilla shows linear branching microcalcifications (circle) spanning approximately 3 cm in ductal distribution within accessory breast tissue in right axilla. Given axillary location of calcifications, calcifications were not amenable to stereotactic core biopsy; however, they could also be visualized sonographically; therefore, ultrasound-guided core biopsy was performed, with pathology ultimately yielding DCIS of low to intermediate nuclear grade.
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Women’s Imaging Review
The ABCs of Accessory Breast Tissue: Basic Information Every Radiologist Should Know Ersilia M. DeFilippis1 Elizabeth Kagan Arleo DeFilippis EM, Arleo EK
OBJECTIVE. Accessory breast tissue, residual breast tissue persisting from embryologic development, is found in up to 6% of the population, most commonly in the axilla along the “milk line.” CONCLUSION. Radiologists should be able to recognize the imaging appearance of this normal variant on multiple modalities, while at the same time understanding that the same spectrum of pathologic processes that occur in normal breast tissue can occur in accessory breast tissue as well.
A
Keywords: aberrant breast tissue, accessory breast tissue, ectopic breast tissue, milk line, supernumerary breasts DOI:10.2214/AJR.13.10930 Received March 20, 2013; accepted after revision August 23, 2013. 1 Both authors: New York-Presbyterian Hospital/Weill Cornell Medical Center, 425 E 61st St, 9th Fl, New York, NY 10065. Address correspondence to E. K. Arleo ([email protected]).
AJR 2014; 202:1157–1162 0361–803X/14/2025–1157 © American Roentgen Ray Society
ccessory breast tissue is defined as “residual [breast] tissue that persists from normal embryologic development” [1]. Also known as ectopic breast tissue, accessory breast tissue can be found in up to 6% of the population [2]. The highest incidence occurs in the Japanese population [3], with the lowest incidence in white individuals [4]. More specifically, ectopic breast tissue is an umbrella term that refers to both supernumerary breasts as well as aberrant breast tissue [3, 5]. Supernumerary breasts are often found anywhere along the “milk line,” an embryologic landmark that runs bilaterally from the anterior axillary folds to the inguinal region and medial thigh [6]. The term “aberrant breast tissue” is defined as “an island of breast tissue usually located in proximity to the normal breast” [4]. Aberrant breasts consist of accessory fragments of breast tissue outside the periphery of the gland [5]. In contrast to supernumerary breasts, aberrant breast tissue lacks organized secretory systems [4]. For the purposes of this article, the term “accessory breast tissue” will be used for consistency. Accessory breast tissue is most commonly located in the axilla, but locations outside the milk line, including the face, posterior neck, chest, middle back, buttock, vulva, flank, hip, shoulder, upper extremities, and posterior and lateral thigh have also been reported [7]. There may be an autosomal-dominant inheritance pattern with incomplete penetrance, but most cases are sporadic [7]. Regardless of the location of the accessory
breast tissue, a patient with accessory breast tissue may be asymptomatic and unaware of the presence of accessory breast tissue. Alternatively, because accessory breast tissue, like normal breast, responds to hormonal influences, it may come to attention during menarche, pregnancy, or lactation [2, 8]. Knowledge about accessory breast tissue has important implications for patient care: If accessory breast tissue is not recognized for what it is, then a normal variant may be misdiagnosed as an abnormality. The most common presumptive diagnoses reported in the literature include lipoma, lymphadenopathy, sebaceous cyst, vascular malformation, and malignancy [9]. At the same time, it is important to recognize that the same spectrum of pathologic processes that occur in normal breast tissue can occur in accessory breast tissue, including benign processes such as fibrocystic changes, mastitis, and fibroepithelial lesions; atypical ductal or lobular hyperplasia; and frank malignancy [2]. If surgical treatment is required, then this raises the questions of the appropriate operative and postoperative management of accessory breast tissue. Given these issues, the objective of this article is to provide a focused, comprehensive, in-depth discussion of the available scientific information on accessory breast tissue. Embryology In the fourth week of human development, a pair of mammary ridges derived from ectoderm form [10]. These ridges, often referred to as the “milk line,” run bilaterally along the
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DeFilippis and Arleo ventral surface of the body from the anterior axillary folds to the medial aspect up the inguinal folds. Normally, these ridges regress except at the site of the breasts [10]. This embryology informs the embryologic theory of accessory breast tissue—namely, that it represents the failure of regression or displacement of the milk line [11–15]. However, this theory fails to account for reported cases of accessory breast tissue outside the milk line, leading to other proposed explanations. In 1950, Hughes [16] proposed that independently migrating nests of primordial breast cells can develop in a completely random manner. Later, Craigmyle [17] alternatively suggested that accessory breast tissue develops from modified apocrine sweat glands. Accessory breast tissue can contain all elements present in normal breast tissue—parenchyma, areola, and nipple [2]. In 1915, a classification system for supernumerary breast tissue, authored by Kajava [18], was published [3, 9]. Class 1 is termed “polymastia” and consists of a complete breast with a nipple, areola, and glandular tissue. Class 2 is a supernumerary breast without an areola, consisting of glandular tissue and a nipple. Class 3 consists of an areola and glandular tissue. Class 4 is glandular tissue only. Class 5 contains a nipple and areola only and is termed “pseudomamma.” Class 6 consists of just a nipple (polythelia), and class 7 consists of just an areola (“polythelia areolaris”). Last, class 8 is termed “polythelial pilosis” and consists of just a patch of hair. Thus, the most common clinical manifestation of accessory breast tissue, fibroglandular tissue in the axilla, is class 4. One or more supernumerary nipples (polythelia) or supernumerary breasts (polymastia) can form along the mammary ridges, and both can enlarge and lactate in response to hormones [10]. Accessory breast tissue is sometimes associated with congenital anomalies of the urogenital system. Estimates of renal anomalies and urologic anomalies in patients with supernumerary nipples range from 11% to 27% [8]. Specifically, accessory nipples can be associated with supernumerary kidneys, failure of renal formation, and renal cell carcinomas [19]. Normal Appearance of Accessory Breast Tissue It is important to recognize the appearance of accessory breast tissue on imaging so that it can be appropriately diagnosed as a normal variant and not a pathologic ab-
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normality. History and physical examination findings suggestive of accessory breast tissue include masses associated with pain or discomfort, milk secretion, and local skin erythema that may be more prominent during pregnancy and lactation [1, 3]. Accessory breast tissue is frequently bilateral, so clinical suspicion should prompt physical examination of the relevant contralateral region [3]. Laboratory analyses add little to no value. Depending on the patient’s age and clinical presentation, imaging evaluation might begin with mammography or ultrasound; alternatively, mammography or ultrasound performed for routine screening or diagnostic purposes might show accessory breast tissue incidentally. Diagnostic breast MRI is occasionally performed in challenging atypical cases or may note accessory breast tissue as an incidental finding. Definitive diagnosis can be established by fine-needle aspiration or excisional biopsy; however, knowledge of the normal appearance of accessory breast tissue on multiple modalities should hopefully preclude such unnecessary invasive procedures [20]. Mammography Figure 1 shows the normal mammographic appearance of accessory breast tissue in the axilla. There may be a small to large amount of fibroglandular elements and densities interspersed with fat that radiographically have the same appearance as normal glandular parenchyma but are located separate from the main breast parenchyma [21]. In contradistinction to the relatively frequent sighting of the axillary tail of Spence, which is a continuous extension of the tissue of the breast that extends into the axilla, accessory breast tissue in the axilla is discontinuous with the main breast parenchyma [21]. However, it should be specifically mentioned that an axillary focal asymmetry on a baseline examination should not automatically be assumed to represent accessory breast tissue. Although this may ultimately be the conclusion, as illustrated in Figure 1, if an axillary focal asymmetry is seen on baseline examination (Fig. 1A), then the patient should be recalled for additional imaging evaluation (Fig. 1B) to prove the hypothesis and exclude other causes (Fig. 2). If an axillary focal asymmetry that represents a change from previous studies is seen, then this finding is especially concerning for a developing malignancy.
Ultrasound Ultrasound is usually the first-choice imaging modality for evaluation of any palpable soft-tissue mass outside the breast and may be the imaging modality of initial choice for a palpable breast mass if the patient is younger than 30 years old [22]. With real-time gray-scale and color Doppler imaging, and without ionizing radiation, sonography can be used to help differentiate a mass of accessory breast tissue from, particularly in the axilla, lipomas, lymphadenopathy, and other pathologic entities [23]. Figure 2 shows the normal sonographic appearance of accessory breast tissue in the axilla. The appearance of accessory breast tissue on ultrasound, irrespective of location, is the same as the appearance of breast tissue within the breast: Fibroductal tissue and lobules of fat are visualized. MRI On MRI, accessory breast tissue can appear as a subcutaneous ill-defined mass or nonmasslike area that has signal intensity and contrast enhancement similar to the rest of the breast parenchyma but is discontinuous with that tissue [9]. Figure 3 shows the normal appearance of accessory breast tissue on MRI. As seen on other modalities as well, the amount of accessory breast tissue within an axilla might be small, moderate, or large; the accessory breast tissue may be symmetric or asymmetric, and its enhancement might be minimal, mild, moderate, or marked similar to the enhancement of the rest of the background parenchyma. In the literature, MRI has been reported to be a useful modality for the diagnosis of ectopic breast tissue in peripubertal or pubertal girls presenting with an axillary mass of uncertain cause [1]. Pathologic Findings in Accessory Breast Tissue Benign All diseases of the breast also occur in accessory breast tissue. Figure 4 illustrates the case of a 37-year-old woman from our institution, 10 days postpartum, who presented with a palpable area of concern in the right axilla that had decreased in size somewhat since delivery. Her medical history was significant for bilateral mastectomies approximately 1.5 years earlier for invasive and in situ ductal carcinoma on the right (which presented as calcifications on mammography) and atypical lobular hyperplasia on the left, followed by bilateral implant reconstruction; genetic testing
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Accessory Breast Tissue was negative. Ultrasound of the right axilla in the palpable area of concern showed a 2.5-cm oval circumscribed mass parallel to the skin with echogenic septations, an echogenic pseudocapsule, and mild internal vascularity. Because of the presence of a new palpable mass in this high-risk patient, ultrasound-guided core biopsy of the right axillary mass was recommended and performed; pathology yielded lactating adenoma, thus supporting the presence of residual axillary accessory breast tissue postmastectomy. Surgical excision was considered, but the patient declined; at clinical follow-up 6 months later, the palpable area of concern had regressed, supporting the pathologic diagnosis of lactating adenoma, the prognosis of which is regression after completion of breast feeding [24]. Cases of other benign pathologic entities occurring in accessory breast tissue have been reported in the literature. For example, several case reports exist of fibroadenomas in accessory breast tissue, including one in a 17-year-old girl who presented with a mobile, firm, and painless mass in the left axilla that gradually increased in size over the course of 3 years. Ultrasound showed a well-circumscribed, homogeneous solid mass that at pathology was a fibroadenoma similar to that seen in normal breast tissue [19]. On gadolinium-enhanced MRI, enhancement of the fibroadenoma in accessory breast tissue can be variable depending on the degree of fibrosis in the tumor [23]. Mammary hamartomas have also been reported to occur in accessory breast tissue. For example, one case report describes a 38-year-old woman with a hamartoma in an accessory breast [23]. Mammography of the accessory breast showed “a circumscribed mass that consists of both soft-tissue and lipomatous elements surrounded by a thin radiolucent zone” and accompanying ultrasound showed an “elongated well-circumscribed mixed echoic mass originating from accessory breast tissue” [23]. Fat necrosis, a benign nonsuppurative inflammatory process of adipose tissue that can occur in response to trauma, has also been reported to occur in accessory breast tissue. One case in the literature describes a 32-year-old woman who underwent chest radiography, which showed indeterminate calcifications in the right axilla for which further imaging was recommended [23]. Sonography showed “poorly defined hypoechoic lesions,” with “curvilinear echogenic foci with posterior shadowing within the mass,”
compatible, in conjunction with the radiographic findings, with fat necrosis [23]. Fat necrosis, hamartomas, fibroadenomas, and lactating adenomas are just four examples of benign pathologic entities that can occur in accessory breast tissue. Malignant There is controversy in the literature as to whether there is an increased risk of malignant transformation in accessory breast tissue compared with pectoral breast tissue. Some studies have suggested an increased incidence of cancer in aberrant breast tissue [4], whereas others suggest that there is no evidence to support this [5]. Investigators have hypothesized that stagnation arising in the lumina of ducts of aberrant breast tissue may play a role in the development of malignancy [4]. In one study, 94% of ectopic breast cancers arose from aberrant tissue as opposed to 6% in supernumerary breasts [4]. Interestingly, the incidence of accessory breast tissue cancer in males has also been reported to be higher than that of pectoral male breast cancer [25]. Cancer in ectopic breasts, stage-for-stage, appears to arise at an earlier age than the same disease in pectoral developmentally normal breast tissue [4]. For example, in one review of 82 cases of ectopic breast cancer in 81 patients, the mean age at diagnosis was 53.3 years (median, 54 years), an average age lower than the average age for pectoral breast cancer [4]; according to statistics from the National Cancer Institute, the median age at diagnosis for breast cancer is 61 years [26]. Furthermore, patients presented with more extensive disease, probably secondary to a delayed diagnosis and less likely because of the disease process itself; however, the possibility that malignancy that exists near the axillary lymph nodes may metastasize earlier than carcinoma of the normal breast has been raised [4, 5, 27]. The most frequently reported malignant disease in ectopic breast tissue is infiltrating ductal carcinoma (79%) [3]. Rare reports of Paget disease, cystosarcoma phyllodes, papillary carcinoma, leiomyosarcoma, and invasive secretory carcinoma also exist [3]. Accessory mammary carcinoma is thought to account for 0.3–0.6% of all breast cancer cases, usually manifesting as an axillary mass [25]. One such example from our institution is shown in Figure 5. Other presentations include suspicious microcalcifications in axillary tissue, as shown in Figure 6. Ac-
cessory breast tissue carcinoma may be asymptomatic and picked up on routine screening, as was the case in both patients shown in Figures 5 and 6, or may be symptomatic, with symptoms similar to carcinoma of the pectoral breast, and be referred to diagnostic mammography. The most common sign seen on physical examination is a palpable lump, but edema and tenderness can also be noted [7]. Interestingly, in the case of the 50-yearold woman in Figure 6, the patient had a long history of bilateral axillary fat pad tissue that has been atypically tender in relation to her menstrual cycles and the presumed diagnosis of bilateral axillary breast tissue had been made in the past. If a mass can be seen sonographically within accessory breast tissue, then tissue sampling can be achieved by ultrasound-guided core biopsy. If accessory breast tissue calcifications are the only imaging finding, then stereotactic core biopsy may be attempted if the calcifications appear amenable. However, if the calcifications are located in accessory breast tissue in the axilla near the chest wall, then they may be difficult to target by this method and if not seen sonographically, surgical excision or lumpectomy may be pursued. The pathology literature reports that it can sometimes be difficult to differentiate breast carcinoma in axillary accessory breast tissue from adenocarcinoma of the sweat glands in the axilla, but identification of estrogen and progesterone receptors can be helpful. Under the microscope, visualization of aberrant normal breast tissue adjacent to an axillary tumor is also used to differentiate primary carcinoma in accessory breast tissue from metastatic cancer to the axilla from an unknown primary site [25, 27]. Cancer of accessory breast tissue can also occur concurrently with cancer in a pectoral breast [4, 28]. In 1976, the first such case was described of a woman who developed primary carcinoma in both breasts as well as in ectopic breast tissue in her vulva [28]. In 1994, Marshall et al. [4] described the case of a woman with lobular carcinoma in a supernumerary breast and infiltrating ductal carcinoma in her left breast. Accessory Breast Tissue Management Most patients with accessory breast tissue are unaware of the presence of accessory breast tissue and are asymptomatic. Thus, although no treatment is required in most cases of accessory breast tissue, in asymptomatic patients who are being screened for breast
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DeFilippis and Arleo cancer or diagnostic patients with a personal history of breast cancer undergoing routine surveillance, the possibility of disease in accessory breast tissue should be considered. The case of the lactating adenoma at our institution proves that this postmastectomy patient had residual axillary accessory breast tissue given that a specific, albeit benign, abnormality arose in that location. It raises questions regarding whether patients with bilateral mastectomies should undergo annual surveillance of the axillae if accessory breast tissue is known and whether preoperative mammography or other breast imaging should definitively comment on the presence or absence of accessory breast tissue to guide the surgeon for a possible wider excision. The treatment of choice for symptomatic accessory axillary breast tissue is surgical excision because removal of the tissue will relieve physical discomfort in the case of a large volume of accessory tissue. Accessory breast tissue may also be removed for cosmetic reasons. In the axilla, accessory breasts can be satisfactorily treated with excision, liposuction, or both [29, 30]. Management of accessory breast tissue cancer should follow the recommendations set forth for pectoral breast cancer of parallel TNM classification [4]. Given the variety of locations of ectopic breast cancers, it is important to understand the lymphatic drainage of the malignant site [4]. Some authors recommend radical mastectomy of the ipsilateral breast, whereas others report that ipsilateral mastectomy does not improve prognosis for ectopic breast carcinoma [7]. Although it might be a concern that patients with an ectopic cancer have an increased risk for developing a second primary cancer, this risk is not considered to be enough to justify prophylactic ipsilateral mastectomy [4]. Others propose that the surgical procedure of choice in the treatment of ectopic breast carcinoma includes wide resection of the tumor with the surrounding tissue, covering skin, and regional lymph nodes [4]. Postoperative treatment of accessory breast tissue is the same as for anatomic breast carcinoma. Estrogen receptor, progesterone receptor, and HER2/neu testing should be performed on accessory breast tissue cancers as is done for pectoral breast cancers [31, 32]. Radiation of the accessory breast tissue tumor site is regularly performed [7], and adjuvant chemotherapeutic and hormonal therapy options should be carried out in accordance with the recommendations for pectoral breast cancers [31].
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Conclusions With accessory breast tissue occurring in up to 6% of the population, most commonly in the axilla but potentially anywhere along the milk line, radiologists should be familiar with its normal appearance on multiple modalities. The clinical significance of accessory breast tissue is that it needs to be recognized for what it is or a normal variant may be misdiagnosed as an abnormality. At the same time, it is important for the radiologist to keep in mind that all diseases of the breast can also occur in accessory breast tissue, including both benign and malignant ones, as this article has illustrated. References 1. Laor T, Collins MH, Emery KH, Donnelly LF, Bove KE, Ballard ET. MRI appearance of accessory breast tissue: a diagnostic consideration for an axillary mass in a peripubertal or pubertal girl. AJR 2004; 183:1779–1781 2. Goyal S, Puri T, Gupta R, Julka P, Rath G. Accessory breast tissue in axilla masquerading as breast cancer recurrence. J Cancer Res Ther 2008; 4:95–96 3. Bakker JR, Sataloff DM, Haupt HM. Breast cancer presenting in aberrant axillary breast tissue. Commun Oncol 2005; 2:117–120 4. Marshall MB, Moynihan JJ, Frost A, Evans SR. Ectopic breast cancer: case report and literature review. Surg Oncol 1994; 3:295–304 5. Rho JY, Juhng SK, Yoon KJ. Carcinoma originating from aberrant breast tissue of the right upper anterior chest wall: a case report. J Korean Med Sci 2001; 16:519–521 6. Hong JH, Oh M-J, Hur J-Y, Lee JK. Accessory breast tissue presenting as a vulvar mass in an adolescent girl. Arch Gynecol Obstet 2009; 280:317–320 7. Youn HJ, Jung SH. Accessory breast carcinoma. Breast Care (Basel) 2009; 4:104–106 8. Velanovich V. Ectopic breast tissue, supernumerary breasts, and supernumerary nipples. South Med J 1995; 88:903–906 9. Sahu SK, Husain M, Sachan PK. Bilateral accessory breast. The Internet Journal of Surgery. www.ispub.com/journal/the-internet-journal-ofsurgery/volume-17-number-2/bilateral-accessorybreast.html#sthash.VP7wyAQQ.dpbs. Published 2008. Accessed February 10, 2013 10. Schoenwolf GC, Bleyl SB, Brauer PR, Francis-West PH. Development of the skin and its derivatives. In: Larsen WJ, ed. Human embryology, 4th ed. Philadelphia, PA: Churchill Livingstone, 2009:193–216 11. de Cholnoky T. Supernumerary breast. Arch Surg 1939; 39:926–941 12. Hamilton WJ, Boyd JD, Mossman HW. Human embryology. Baltimore, MD: Williams & Wilkins, 1945 13. Haagensen CD. Diseases of the breast, 2nd ed. Philadelphia, PA: Saunders, 1971
14. Schultz A. Pathologische anatomie der brusdruse: handbuch der speziellen. In: Henkee F, Lubarsch O, eds. Pathologischen anatomie and histologie, vol. VII. Berlin, Germany: Springer-Verlag, 1933 15. Hanson E, Segóvia J. Dorsal supernumerary breast: case report. Plast Reconstr Surg 1978; 61:441–445 16. Hughes ES. The development of the mammary gland: Arris and Gale Lecture, delivered at the Royal College of Surgeons of England on 25th October, 1949. Ann R Coll Surg Engl 1950; 6:99–119 17. Craigmyle MB. The apocrine glands and the breast. New York, NY: Wiley, 1984:49–55 18. Kajava Y. The proportions of supernumerary nipples in the Finnish population. Duodecim 1915; 31:143–170 19. Mukhopadhyay M, Saha AK, Sarkar A. Fibroadenoma of the ectopic breast of the axilla. Indian J Surg 2010; 72:143–145 20. Farcy DA, Rabinowitz D, Frank M. Ectopic glandular breast tissue in a lactating young woman. J Emerg Med 2011; 41:627–629 21. Adler DD, Rebner M, Pennes DR. Accessory breast tissue in the axilla: mammographic appearance. Radiology 1987; 163:709–711 22. American College of Radiology website. ACR Appropriateness Criteria for palpable breast masses. www.acr.org/~/media/ACR/Documents/AppCriteria/Diagnostic/PalpableBreastMasses.pdf. Published 1996. Updated 2012. Accessed June 27, 2013 23. Kim EY, Ko EY, Han BK, et al. Sonography of axillary masses: what should be considered other than the lymph nodes? J Ultrasound Med 2009; 28:923–939 24. Dähnert W. Radiology review manual, 6th ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2011 25. Yamamura J, Masuda N, Kodama Y, et al. Male breast cancer originating in an accessory mammary gland in the axilla: a case report. Case Report Med 2012; 2012:286210 26. National Cancer Institute website. SEER stat fact sheets: breast. seer.cancer.gov/statfacts/html/breast. html. Accessed June 26, 2013 27. Cogswell HD, Czerny EW. Carcinoma of aberrant breast of the axilla. Am J Surg 1961; 27:388–390 28. Guerry RL, Pratt-Thomas HR. Carcinoma of supernumerary breast of vulva with bilateral mammary cancer. Cancer 1976; 38:2570–2574 29. Aydogan F, Baghaki S, Celik V, et al. Surgical treatment of axillary accessory breasts. Am Surg 2010; 76:270–272 30. Fan J. Removal of accessory breasts: a novel tumescent liposuction approach. Aesthetic Plast Surg 2009; 33:809–813 31. Gutermuth J, Audring H, Voit C, Haas N. Primary carcinoma of ectopic axillary breast tissue. J Eur Acad Dermatol Venereol 2006; 20:217–221 32. Madej B, Balak B, Winkler I, Burdan F. Cancer of the accessory breast: a case report. Adv Med Sci 2009; 54:308–310
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Fig. 1—Normal appearance of accessory breast Breast Accessory tissue on mammography. A, 37-year-old asymptomatic woman presented for baseline screening mammography. Asymmetry (circle) is seen on right, upper hemisphere, posterior plane on mediolateral oblique view. B, Patient was recalled for finding shown in A. Mammogram shows patch of pliable fibroglandular tissue with interspersed fat discontinuous with majority of breast tissue more inferiorly, which is consistent with accessory breast tissue, and benignappearing axillary lymph nodes. To confirm these findings, ultrasound was performed (Fig. 2).
A
Fig. 2—Normal appearance of accessory breast tissue on ultrasound of 37-yearold asymptomatic woman (same patient as Fig. 1). Gray-scale image targeted to right axilla shows original mammographic area of concern. Arrow indicates dermis, half bracket indicates retromammary layer, and bracket indicates accessory breast tissue between dermis and retromammary layer.
Tissue
B
Fig. 3—Axial image from contrast-enhanced (12 mL of gadolinium) VIBRANT (Volume Image Breast Assessment, General Electric Company) fast 3D gradientecho sequence with T1-weighting and fat suppression (TR/TE, 5.76/2.752; flip angle, 10°) of 41-year-old woman shows normal appearance of accessory breast tissue (bracket). Small to moderate amount of accessory breast tissue is seen in left axilla with mild enhancement.
Fig. 4—37-year-old woman with bilateral mastectomies (for invasive and in situ ductal carcinoma on right and atypical lobular hyperplasia on left) who presented for surveillance imaging was found to have lactating adenoma in residual axillary accessory breast tissue. Gray-scale image of right axilla shows 2.5-cm palpable, oval, circumscribed mass parallel to skin with echogenic septations, echogenic pseudocapsule, and mild internal vascularity. Ultrasound-guided core biopsy was performed, with pathology yielding lactating adenoma.
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DeFilippis and Arleo
A
B
C
Fig. 5—88-year-old woman with infiltrating and in situ lobular carcinoma in axillary accessory breast tissue presenting as mass. A, Bilateral mediolateral oblique (MLO) images from screening mammography show asymmetry in left axillary breast tissue (circle). B, Spot compression view of left axilla in MLO projection shows high-density irregular mass with spiculated margins. C, Ultrasound image of left axilla targeted to mammographic abnormality shows 9-mm hypoechoic irregular mass with spiculated margins (cursors); core biopsy was performed, with pathology yielding infiltrating and in situ lobular carcinoma (low nuclear grade).
Fig. 6—50-year-old woman with ductal carcinoma in situ (DCIS) in axillary accessory breast tissue presenting as microcalcifications. Screening mammogram (not shown) showed faint microcalcifications in accessory breast tissue in right axilla, and patient was recalled for additional imaging. Spot magnification view of right axilla shows linear branching microcalcifications (circle) spanning approximately 3 cm in ductal distribution within accessory breast tissue in right axilla. Given axillary location of calcifications, calcifications were not amenable to stereotactic core biopsy; however, they could also be visualized sonographically; therefore, ultrasound-guided core biopsy was performed, with pathology ultimately yielding DCIS of low to intermediate nuclear grade.
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