Tumors arising from an axillary accessory breast: a 10-year retrospective cohort study at a single center

Abstract

Purpose

Pathologic lesions may occur in an axillary accessory breast (AAB). This study aimed to evaluate the characteristics of tumors arising from AABs and to recommend appropriate treatment.

Methods

This retrospective study involved 3,544 women (18–65 years old) with AAB at Damsoyu Hospital in Korea from 2014 to 2023. The patients were divided into an AAB with benign tumors (TAAB) group and an AAB without tumors (AAB) group, and the tumors’ pathologies were reviewed. A core biopsy was performed on tumors with possible malignancy identified by preoperative ultrasonography. All patients underwent complete excision of accessory mammary gland (AMG) tissue, including tumors. The postoperative results were checked 6 months after surgery.

Results

Fifty-two out of 3,554 patients had tumors confirmed by preoperative ultrasonography. Preoperative core biopsies were performed on 11 patients. Two patients had malignant tumors (invasive ductal carcinoma) identified by core biopsy. Fifty patients had benign tumors identified by postoperative pathological analysis (46 fibroadenomas, 2 fibrocystic changes, and 2 sclerosing adenoses). Carcinoma in situ was confirmed in 2 patients using postoperative pathological analysis. No patients in either group developed tumors in the axilla during the follow-up period. All patients were satisfied with the axillary pain relief and the disappearance of bulging lesions.

Conclusion

We recommend a core biopsy if preoperative ultrasonography indicates a possibly malignant tumor. AAB patients may experience tumors, pain, and bulging appearance of an AMG; thus, complete AMG excision is necessary.

INTRODUCTION

Accessory breasts occur mostly in the axilla [1]; thus, it is termed axillary accessory breast (AAB). Some patients require treatment for associated cyclic axillary pain or aesthetic concerns related to the bulging appearance [2,3,4]. Patients rarely present with the main complaint of a palpable axillary mass, which has been described in case reports as a benign tumor in an AAB (TAAB) [5,6]. These tumors are mostly benign, but malignant tumors have also been reported [7,8]. The main purpose of an AAB excision is to reduce pain and correct appearance, and its second purpose is to treat a TAAB.

Confirmation of a TAAB is possible with ultrasonography [9], and a core biopsy can be performed for tumors with possible malignancy using preoperative ultrasonography. If a core biopsy confirms a malignant tumor, cancer treatment should be performed [10]. Many studies have found that AAB treatments reduce axillary pain or its bulging appearance [11,12]. The AAB classification system is based on the severity of the external appearance and the recommended treatment for complete accessory mammary gland (AMG) excision [2,12].

Two methods can be considered for the treatment of TAAB: only removing the tumor, as with the treatment of a pectoral normal breast (PNB) tumor, and removing the entire AMG, including the tumor. Although several case studies describing treatment for TAABs have been published [5,13], to the best of our knowledge, no guidelines have been published, and no large studies have been performed on TAABs. PNB tumors are usually asymptomatic; however, TAABs are easily palpated and often accompanied by pain and a bulging appearance because of the AMG. To treat TAABs successfully, it is crucial to determine whether the problem is limited to the tumor or is accompanied by pain and aesthetic concerns about the bulging appearance caused by the AMG tissue [2]. Most AAB patients have axillary pain and a bulging appearance, regardless of the presence of a tumor [5]. The treatment of a palpable tumor in the PNB involves the excision of the tumor and the preservation of the mammary gland [13], but the treatment of a TAAB should resolve the pain and aesthetic concerns caused by the AMG tissue [5]. Therefore, a complete excision of the AMG tissue and TAAB is necessary to treat AAB.

This study compared the baseline patient characteristics, AAB characteristics, and surgical outcomes of patients with AAB with and without a tumor who were undergoing surgical excision. We also monitored the patients for the recurrence of TAABs.

METHODS

Ethics statement

All procedures performed in studies involving human participants were in accordance with the ethical standards of our institutional and national research committee and the 1964 Helsinki Declaration and its later amendments, or with comparable ethical standards. Written informed consent was provided by all the patients included in this study. This study was approved by the Institutional Review Board of Damsoyu Hospital (No. DSY-2024-002). Informed consent was obtained from all individual patients or their parents and guardians.

Patient selection and clinical assessment

This retrospective cohort study analyzed the data of 3,544 patients with an AAB treated at Damsoyu Hospital in Seoul, Korea from January 2014 to December 2023 (Fig. 1). The classification of the AAB was performed in accordance with Damsoyu–Lee classification [2]. All patients underwent preoperative ultrasonography and postoperative pathological confirmation of lesions in the AAB. Most of the patients included in this study were undergoing mammography examinations at other institutions within the Korean periodic health checkup system. Therefore, mammography was not performed preoperatively unless there were special circumstances. The ultrasonographic findings of a TAAB were characterized using the breast imaging reporting and data system (BIRADS) (Fig. 2). All the patients with a BIRADS category ≥4 mass underwent core biopsy before surgery. A pathologic examination was performed on the entire AMG specimen removed from all surgical patients. The TAAB diagnoses were confirmed by a final pathologic examination of the specimen. When cancer was diagnosed pathologically, we referred the patient to a tertiary center. Eleven cases had tumors with a BIRADS category ≥4 found on preoperative ultrasonography. Two of the 11 cases diagnosed with invasive cancer were referred to a tertiary hospital. Specimen pathology identified 2 patients with carcinoma in situ. We divided the patients into the AAB group (AAB without tumor, n = 3,490) and the TAAB group (AAB with benign tumor, n = 50) according to the presence of a benign tumor in the AAB. All patients underwent complete excision of the AMG tissue, including the tumor (Fig. 3).

Fig. 1. Flowchart of patient enrollment. During the study period, 3,544 patients with an axillary accessory breast (AAB) visited our hospital, and 52 patients had tumors arising from the accessory mammary gland confirmed by preoperative ultrasonography. Tumors of breast imaging reporting and data system (BIRADS) ≥4 were found using preoperative ultrasonography in 11 cases. Two of the 11 cases diagnosed with invasive cancer were referred to a tertiary hospital. An assessment of specimen pathology confirmed carcinoma in situ in 2 patients. We divided the patients into an AAB group (AABs without a tumor, n = 3,494) and a TAAB group (AABs with a benign tumor, n = 50) according to the presence of a tumor in the AAB.

Fig. 2. Sonographic findings of an axillary accessory breast. (A) No abnormal findings, only accessory mammary glands are visible. (B) Breast imaging reporting and data system (BIRADS) 3. (C) BIRADS 4. (D) BIRADS 5 tumors within the accessory mammary gland.

Fig. 3. A fibroadenoma measuring 2.0 cm in the axillary accessory breast in a 44-year-old woman who underwent surgery. (A) Preoperative frontal appearance with arms abducted. (B) Fibroadenoma is present in the accessory mammary gland (AMG) on ultrasonography. (C) A 1-cm incision along the axillary skin crease. (D) Accessory mammary gland tissue, including the tumor, was removed. A fibroadenoma (black arrow) is visible within the removed AMG. (E) One-month postoperative frontal abduction view.

All patients completed satisfaction surveys evaluating their appearance and axillary pain 6 months after surgery. We evaluated tumor recurrence and AAB recurrence by symptoms, physical examination, and ultrasonography. Overall satisfaction with the decreased level of axillary pain and the alleviation of aesthetic concerns was determined for all patients using a 5-point Likert scale [14].

Surgical technique and follow-up

We used a previously reported AAB excision method involving a 1-cm incision on the axillary crease and performed all procedures with the patients under general anesthesia [2,10]. First, we instilled a tumescent solution through an incision into the accessory breast tissue, followed by liposuction with a power-assisted device. After the liposuction of the fat layer, we performed a complete AMG excision and closed the incision with subcuticular absorbable sutures. An external drain was not inserted. Follow-up examinations were routinely performed at 1, 3, and 6 months postoperatively.

Statistical analysis and assessment methods

All statistical analyses were performed using R software ver. 3.6.1 (The R Foundation). Continuous variables were analyzed using the t-test for normally distributed data and the Wilcoxon rank-sum test for non-normally distributed data. Categorical variables were compared using the chi-square test or Fisher exact test, depending on the expected frequencies in each cell. All tests conducted were 2-tailed. The satisfaction score was measured according to scar, pain, and cosmesis level scores 6 months postoperatively using a 5-point Likert scale. A P-value ≤0.05 in the univariate analysis was considered statistically significant.

RESULTS

Comparing clinical characteristics and outcomes in patients with accessory axillary breasts with and without benign tumors

The patients’ clinical characteristics and surgical outcomes are summarized in Table 1. We compared the baseline patient characteristics in the AAB and TAAB groups and found no differences in age, AMG tissue weight, or family history. Forty-nine of the 50 patients in the TAAB group experienced cyclic axillary pain. The postoperative complication rate, redo operation rate, and satisfaction score for the 2 groups were not significantly different. No patients in either group developed AAB or tumor recurrence in the axilla during the follow-up period.

Table 1. Clinical characteristics and surgical outcomes in benign tumors in AABs and non-tumors in AABs.

Values are presented as number only, mean ± standard deviation (range), or number (%).

AAB, axillary accessory breast; AMG, accessory mammary gland; NA, not available.

^a)Continuous variables were analyzed using the t-test for normally distributed data and the Wilcoxon rank-sum test for non-normally distributed data. Categorical variables were compared using the chi-square test or Fisher exact test, depending on the expected frequencies in each cell. All tests were 2-tailed. ^b)The satisfaction score was measured according to scar, pain, and cosmesis level scores 6 months postoperatively using a 5-point Likert scale.

Clinical characteristics of benign tumors in accessory axillary breasts

The characteristics and surgical outcomes of the 50 patients in the TAAB group are summarized in Table 2. Bilateral TAABs were present in 1 patient, right-sided TAABs in 27 patients, and left-sided TAABs in 22 patients. The tumors were as follows: 46 fibroadenomas, 2 fibrocystic changes, and 2 sclerosing adenoses. All patients were satisfied with the degree of postoperative pain relief, the disappearance of palpable lesions, and cosmetic improvement.

Table 2. Clinical characteristics and surgical outcomes of benign TAAB.

Data are presented as number only or number (%).

TAAB, axillary accessory breast with benign tumors; BIRADS, breast imaging reporting and data system.

Clinical characteristics of malignant tumors

The characteristics of the 4 malignant tumors are summarized in Table 3. Two patients with malignant tumors (invasive ductal carcinoma) identified via core biopsy were referred to a tertiary hospital. Two patients were diagnosed with carcinoma in situ, one with ductal carcinoma in situ, and one with lobular carcinoma in situ, as assessed by specimen pathology (Fig. 4). Carcinoma in situ was not detected using preoperative ultrasonography but was confirmed by postoperative specimen pathologic examination. Two patients diagnosed with invasive cancer before surgery and 2 patients diagnosed with carcinoma in situ after surgery were transferred to a tertiary hospital, and subsequent treatment and follow-up were performed at that hospital.

Table 3. Clinical characteristics of malignant TAABs.

TAAB, axillary accessory breast with benign tumors; AMG, accessory mammary gland.

Fig. 4. (A) Photographs of a 49-year-old woman who underwent axillary accessory breast (AAB) surgery. There was no palpable mass other than the accessory mammary gland (AMG) lump upon preoperative physical examination. There was no tumor on preoperative ultrasonography, and no macroscopic tumor was observed in the removed AMG. The final specimen pathology confirmed that it was a multifocal lobular carcinoma in situ (LCIS). (B) Photographs of a 35-year-old woman who underwent AAB surgery. There was no palpable mass other than the AMG lump upon preoperative physical examination. There was no tumor on preoperative ultrasonography, and no macroscopic tumor was observed in the removed AMG. The final specimen pathology was confirmed as a 0.3-cm ductal carcinoma in situ (DCIS). Hematoxylin and eosin (H & E) stain, ×100.

DISCUSSION

Benign and malignant tumors may occur via pathological mechanisms in an AAB, as they do in the PNB [15]. Among benign tumors, fibroadenoma accounts for the largest proportion [5], whereas malignant AAB tumors are rare [7,10,16,17].

The main symptom of a TAAB is a palpable mass, and some patients present for evaluation for fear of cancer. When we examined the patients with TAABs, there were usually no symptoms directly related to the tumor; however, most patients had cyclic pain and discomfort due to protruding appearance caused by the AMG tissue. In the present study, 49 patients who underwent TAAB surgery experienced cyclic axillary pain. Such pain often occurs with cyclic swelling during menstruation and pregnancy, and the severity may be so great that patients request surgical treatment [2,18]. In this study, invasive malignant tumors and benign tumors were identified as lesions on preoperative ultrasonography, but 2 patients with carcinoma in situ were not detected on ultrasonography and were finally confirmed by pathological examination of the specimen. In this study, 2 patients were diagnosed with invasive malignant cancer using a preoperative core biopsy. Thus, a preoperative ultrasonographic examination must be performed, and tumors with BIRADS ≥4 must undergo a core biopsy to rule out cancer. A pathological examination of the AMG specimen must also be performed because carcinoma in situ might not be detected by a preoperative ultrasonographic examination.

Several studies have found that the aim of AAB surgery is to improve the patient’s appearance or relieve axillary pain [2,12,19]. The complete treatment of an AAB involves removing all AMG tissue, which may be accompanied by liposuction to reduce scarring [2,20]. A complete excision of the AMG tissue should be performed to prevent the recurrence of AAB [12,21]. In cases of patients with TAAB, axillary pain and discomfort related to the protruding appearance of AMG are often present; thus, complete removal of the entire AMG, including the tumor, is recommended rather than removing only the tumor [5,8]. In this study, the satisfaction surveys administered 6 months postoperatively revealed scores of ≥4.7 for axillary pain and aesthetic improvement in both groups, indicating that the cyclic axillary pain and aesthetic concerns were almost eliminated.

However, it should be noted that tumors may recur in the remaining AMG tissue. A previous study showed a 15% recurrence rate 5 years after fibroadenoma removal from the PNB [22]. In this study, the mean follow-up period was 75 months in the TAAB group and 68 months in the AAB group, with no patients developing tumor recurrence. It should also be noted that the removal of all AMG tissue can reduce tumor recurrence. In this study, no patient developed axillary pain during the postoperative follow-up period. Therefore, the complete treatment of a TAAB requires tumor excision and a complete excision of the AMG tissue. This study is clinically meaningful in that it is the first large study to present treatment guidelines for TAABs.

This study has several limitations. Ultrasonography was performed as a preoperative image analysis, but MRI or CT could have been helpful. Patients with invasive malignant cancer were transferred to a tertiary hospital; therefore, the surgical results are unknown. Thus, multicenter studies involving larger numbers of patients are necessary.

In conclusion, we recommend performing a core biopsy when preoperative ultrasonography identifies a possibly malignant tumor. AAB patients experience problems related to the tumor, involving a bulging appearance and pain related to the AMG. Thus, complete AMG excision is necessary. Carcinoma in situ in AAB may not be detected on preoperative ultrasonography; therefore, a pathologic examination of the specimen must be performed.