Author's: Sá, Margarida¹; Martins, Ana Rita²; Amaral, Patrícia²; Ascensão, Carlos²; Fidalgo, Pedro²; Sidiropoulou, Zacharoula²  

Affiliations: 1 – Plastic, Reconstructive and Aesthetic and Maxillofacial Surgery Department of Hospital Egas Moniz - Unidade Local de Saúde Lisboa Ocidental (ULSLO);  

2 - Breast Unit, General Surgery Department – Unidade Local de Saúde Lisboa Ocidental (ULSLO);  

Corresponding author: Margarida Sa; msa@ulslo.min-saude.pt; ORCID: https://orcid.org/0000-0002-2976-2784  

Hospital Egas Moniz, Unidade Local de Saúde Lisboa Ocidental 

Rua da Junqueira 126, 1349-019, Lisboa, Portugal 

Declarations: The authors did not receive support from any organization for the submitted work. The authors have no relevant financial or non-financial interests to disclose.

ABSTRACT 

Ectopic breast tissue occurs due to the failure of involution of mammary ridges during gestation, along the milk line, extending from the axillary region to the groin. Axillary accessory breast (AAB) occurs in 2–6% of women and it can potentially undergo the same physiological processes, such as cyclical pain during menstruation, swelling, and lactation, or pathologic processes such as intraductal papilloma, fibroadenoma, and carcinoma. Fibroadenomas are among the most common benign tumors of the normally located breast in women under 30 years of age and feature a proliferation of both epithelial and stromal elements. Development of fibroadenomas in axillary accessory breast tissue is extremely rare, with fewer than 40 cases worldwide reported in the literature. They can undergo periodic enlargement, and the main symptoms are cyclic pain and anxiety due to cancerofobia. The clinical history and a detailed objective exam are fundamental to exclude other differential diagnoses for axillary masses. Bilateral ultrasonography and core biopsy are recommended preoperatively. Up to date, there are no guidelines for the treatment for fibroadenomas arising into AABs and no large studies have been published. Treatment of a fibroadenoma in an AAB involves complete excision of both accessory breast tissue and the fibroadenoma. This approach might resolve pain and aesthetic concerns, by removing all the ectopic breast tissue it is possible to prevent new fibroadenomas.  

Keyword's: fibroadenoma, axillary breast tissue, ectopic breast, surgery

Abbreviations: Axillary accessory breast (AAB) 

INTRODUCTION

During the 6th week of embryonic development, mammary gland development begins as two ectodermal thickenings along the sides of the embryo, extending from the axillary region to the groin, representing the mammary milk lines [1]. 

In normal development, most of the embryologic mammary tissue involutes along the milk line, except for two segments in the pectoral region, which later will become breasts. The failure of normal apoptotic regression of mammary ridges during gestation leads to accessory breast developing usually along the milk line, creating a supranumerary breast, or ectopic breast, or polymastia [1,2].  

In general population, the occurrence of ectopic breast tissue ranges from 0.22% to 6% [1]. 67% of accessory breast tissue is present in the thoracic and abdominal portion of the milk line, with another 20% occurring in axilla [2]. 

There is a second hypothesis proposed for the development of ectopic breast tissue which is the development from the modified apocrine sweat glands. While the first hypothesis is the most known and accepted, the second theory explains the occurrence of accessory breast outside the milk line in atypical locations, such as face, posterior neck, thigh, shoulder, and upper extremities [1]. 

Accessory breast tissue can occur with or without a nipple–areola complex and is subject to hormonal response. It can potentially undergo the same physiological processes as the normally located breast, including cyclical pain, swelling, and lactation [1-3]. It can also undergo pathologic processes such as intraductal papilloma, fibroadenoma, and carcinoma. Of these, carcinoma is the most reported [1].  

An axillary accessory breast (AAB) occurs in 2–6% of women. The periodic enlargement of an AAB and cyclic pain are the primary reasons for surgical treatment. Bilateral ultrasonography is recommended for the preoperative diagnosis. A palpable mass may also be an indication for surgical treatment [3,4]. 

Fibroadenoma is a benign biphasic tumor featuring a proliferation of both epithelial and stromal elements. The exact etiology and pathophysiology is poorly understood, but it is generally thought to be under estrogen hormone control [2]. Fibroadenomas are classified as simple, complex, giant, myxoid or juvenile. Simple fibroadenomas are the most common type, making up to 86% of cases [5]. Clinically, simple fibroadenoma typically presents as a painless, firm, slow-growing, mobile, and well-defined breast mass, although occasionally it can cause cyclical pain [1]. 

Fibroadenomas are among the most common benign tumors of the normally located breast in women under 30 years of age. In the adolescent population, the overall incidence of fibroadenoma is 2.2% and account for 68% of all breast masses and 44–94% of biopsied breast lesions [1,2]. 

Fibroadenomas do not carry a risk of breast cancer, but patients with complex fibroadenomas are more likely to have concomitant high-risk histological changes which are themselves associated with increased risk of malignancy [5]. 

Despite fibroadenoma being a common breast lesion, it is rare to develop over the accessory breast tissue in axilla. Fewer than 40 cases of fibroadenoma in accessory breasts have been reported worldwide in the literature [2,6]. 

Patients with fibroadenomas in AAB normally present a palpable mass, cyclic axillary pain, and aesthetic concerns that must be addressed. Patients can often present cancerofobia. 

First-line investigation of a fibroadenoma follows the triple assessment protocol which includes clinical examination, imaging and tissue biopsy [5]. Investigation with ultrasonography is the first line in women under 40 years old and during pregnancy and lactation, and key features include solid, round or oval, well-circumscribed masses, with or without lobulated features with the width/heigh ratio >1. Biopsy is not indicated in all cases. For patients under the age of 25 years, the Royal College of Radiologists (2019) recommend that biopsy of a presumed fibroadenoma is not required if ultrasound imaging satisfies the typical characteristics [7]. If suspicious or malignant features are present, a core biopsy under image guidance is recommended [5].  

Fibroadenomas are predominantly treated conservatively, with clinical review, reassurance and observation. However surgical intervention is indicated by the presence of one or more of the following features: presence of symptoms, a diameter greater than 2 cm, rapid growth, complex characteristics, disease recurrence or patient anxiety [2,5,8]. 

CASE PRESENTATION

A 41 years-old female patient was referred to a Senology consultation by her family doctor, in Hospital São Francisco Xavier, Lisbon, with suspicious findings of a mass on her right axilla.  

In July 2023, a breast ultrasound has been performed that revealed a solid hypoechoic lump with well-defined contours in the transition from the upper outer quadrant of the right breast to the axilla, measuring approximately 14 mm. There was also detected an exuberant axillary lump, which had increased in size to 27 mm (from 17 mm). Left axilla was negative. She also had a mammogram and a final BI-RADS 4 classification. 

The patient had no relevant personal or family history and was not under any medication. Clinically, the patient presented painful palpation of the right breast, with a palpable deep lump in the upper outer quadrant of the right breast and a firm, well defined, mobile lump in the right axilla measuring approximately 2 cm. Skin over the mass was normal with no nipple, areola, or ulceration. 

Due to the findings, she underwent a breast and axilla ultrasound guided biopsy. The anatomopathological results showed in both cases fragments of breast tissue without evidence of neoplastic tissue and the presence of some septa that could be compatible with a benign biphasic lesion of the breast: fibroadenomas.  

Due to dimensions and pain, the patient was proposed to right axillary mastectomy and excision of the mammary fibroadenoma. Through a superiorly convex arciform incision in the right axilla, there was performed right axillary mastectomy with excision in block of both the axillary and breast fibroadenoma. There were no complications intra or post surgery. Histopathology was compatible with fibroadenomas inserted in the breast parenchyma with apocrine metaplasia and foci of adenosis.  

The patient was evaluated 3 months after the surgery, with normal healing progress and a satisfactory aesthetic outcome.  

Fig. 1 - Right axillary acessory breast

Fig. 2 - Gross specimen: well-circumscribe, white-grey in colour with lobulated contours, 4,2x3,5x2,5 cm mass 

Fig. 3 - Follow-up 3 months after surgery 

DISCUSSION

Hereby we present a case of a 41 years-old patient with a right axilla lump. A mass in the axillary region has several differential diagnostics and represents a moment of increased anxiety for the patients. Differential diagnoses include lymphadenopathy (neoplastic, inflammatory or infectious), lipoma, neuroma, skin lesions (various cystic and tumorous lesions), axillary tail of Spence, accessory breast tissue and lesions arising from it [1,2].  

This case represents the importance of a complete anamnesis, clinical history and a detailed clinical exam. It is fundamental to rule out symptoms such as pain, fever, weight loss, night sweating. Personal and family history of cancer is also important. Accessory breast tissue is sometimes associated with other congenital anomalies of the urinary and cardiovascular systems, so physical examination is also of important role [1]. 

The diagnostic and therapeutic protocol for tumors in accessory breast tissue is similar to that of a normal breast mass. However, owing to its rarity and lack of awareness, diagnosis may be delayed, thus making timely treatment more difficult. When tumors or lumps are detected along the mammary line, breast tissue should be considered during the investigation. Core biopsy  helps to the proper diagnosis, to rule out the other differential diagnosis and to guide the proposed approach [1].  

In 1925, Kajava developed the accessory breast classification system still used nowadays (Appendix 1). Our patient presented just glandular breast tissue without any nipple-areola complex, being classified as Kajava class IV.   

Patients with a fibroadenoma in an AAB are at increased risk fibroadenomas on the normal breast [4], such as the patient we present.  

Up to date, there are no guidelines for the treatment for fibroadenomas arising from AABs, no large studies have been published [4]. Treatment of a palpable fibroadenoma in the normal chest breast involves excision of the fibroadenoma and preservation of the mammary gland, but treatment of a fibroadenoma in an AAB involves complete excision of both accessory breast tissue and the fibroadenoma. This may resolve the pain and aesthetic concerns caused by the AAB. With this approach, it is possible to prevent local fibroadenoma recurrence in the AAB. Surgeons should also consider the high incidence of concurrent fibroadenomas in the normal breasts on the chest [4].  

Management of fibroadenomas of the normal breast is typically conservative, although some options of medical management have been proposed, such as metformin to downsize, and tamoxifen to reduce the incidence of fibroadenomas in woman at high risk of breast cancer [5]. These options are rarely applied in the present. Some minimally invasive surgical options with good cosmetic results have been described, such as ultrasound-guided vacuum-assisted excision for fibroadenomas smaller than 2 cm, and less commonly used cryoablation, image-guided radiofrequency excision biopsy or interstitial laser therapy [5]. 

Despite these new approaches, complete surgical excision is still the most common approach and after full excision, recurrence in young women is rare. No routine follow up is required for fibroadenoma post-excision, as long as the histology is benign.  

Complete treatment of an AAB involves removing the entire accessory mammary tissue, which might be accompanied by liposuction to reduce scars. Complete excision of the axillary accessory breast tissue should be performed to prevent recurrence [4]. 

The most common complications after removal of AAB include incomplete excision, seroma, pain, intercostal nerve injury, scar defect and contour deformity, which can be avoided with careful planning, attention to contour, and meticulous dissection [9]. 

CONCLUSION

Axillary accessory breast occurs in 2–6% of women. It can undergo the same physiological and pathologic processes as the normally located breast, including development of fibroadenomas. Fibroadenomas are among the most common benign tumors of the normally located breast in women under 30 years of age, but fewer than 40 cases worldwide of fibroadenoma in accessory breasts have been reported in the literature. They present as a palpable mass, cyclic axillary pain, aesthetic concerns and patient anxiety associated with cancerofobia. Woman with fibroadenomas in AAB should undergo clinical examination, bilateral ultrasonography, and tissue biopsy when indicated. Treatment involves complete excision of both accessory breast tissue and the fibroadenoma. This may resolve the pain and aesthetic concerns caused by the AAB, preventing fibroadenoma recurrence. More studies are necessary to clarify the management and surveillance of patients with axillary accessory breast tissue and lesions associated with it.  

Appendix 1: Kajava classification for accessory breast tissue [1] 

REFERENCES

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7-Guidance on screening and symptomatic breast imaging. 2019, 4th: Available from: https://www.rcr.ac.uk/system/files/publication/field_publication_files/bfcr199-guidance-on-screening-and-symptomatic-breast-imaging.pdf.

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