Introduction
Granulomatous mastitis (GM) is a rare inflammatory condition of the breast that primarily affects women of childbearing age, often with a history of breastfeeding. GM is categorized into idiopathic or primary GM and secondary GM (1,2). It primarily involves the mammary gland, although in rare cases, it can develop in accessory breast tissue (2). While the exact cause of GM remains unclear, the leading hypothesis suggests an autoimmune origin. Various factors, including medications, diabetes, trauma and smoking, may trigger the inflammatory response. However, the strongest associations with GM are pregnancy, lactation and hyperprolactinemia. The disease accounts for <1% of breast biopsies (3). Despite being a benign disease, GM is frequently difficult to detect, as it often masquerades as breast carcinoma, which is the primary concern at the clinical stage (4). Its locally aggressive character causes long-term discomfort and distress for affected patients. Its non-specific imaging findings can lead to delayed diagnosis, misinterpretation and potentially unnecessary invasive procedures. Only a limited number of cases of GM in axillary breast tissue have been documented (1,2). The present report describes the case of a 43-year-old female patient with GM in the accessory breast. The report has been organized following the CaReL guidelines, and only reliable, peer-reviewed sources were included, while excluding any untrustworthy references or data (5,6).
Discussion
Accessory breast tissue arises along the embryonic mammary ridge, extending from the axilla to the pubic region, and is susceptible to the same pathological conditions as normally located breast tissue (1). The frequently reported conditions in accessory breast tissue include cancer, mastitis, fibroadenomas, phyllodes tumors and fibrocystic changes (7). The leading hypothesis regarding the pathogenesis of GM suggests that an autoimmune response is initiated within the lobules of the breast parenchyma following ductal injury. This triggers a localized inflammatory reaction in the connective tissue, promoting the recruitment of macrophages and lymphocytes, ultimately resulting in a noncaseating granulomatous response (3).
The influence of ethnicity on GM remains a subject of debate. Vall et al (3) reported no specific ethnic predisposition. By contrast, the studies by Yuan et al (8) and Deng et al (9) indicated a higher prevalence of GM in Middle Eastern populations compared to Western countries. Consistent with the present case, GM predominantly affects women of reproductive age, particularly those with a history of breastfeeding. Among the 7 cases reviewed herein, 4 patients had a prior history of breastfeeding, with an average duration of 22.7 months (Table I) (1-4,7,10,11). However, Nakamura et al (7) and Rajendran et al (10) documented cases of GM in women without a history of breastfeeding.
Bilateral involvement in GM is rare, as the condition typically presents unilaterally (1). In the patient in the present study, a breast ultrasonography identified two distinct heterogeneous collections within the left axillary breast, accompanied by mild edema and skin sinuses. These imaging findings were consistent with the characteristic manifestations of GM, which commonly include mass formation, skin changes and the development of a sinus tract. Systemic symptoms, such as fever, remain uncommon in GM cases (1). Among the cases reviewed herein, all were unilateral, with fever reported in only 1 patient. Pain was the reported symptom in 6 cases, whereas erythema was observed in only 2 cases.
The diagnosis of GM requires a well-coordinated multidisciplinary approach involving clinicians, radiologists and pathologists, as demonstrated in the present case report. This is particularly critical given that cases with clinical deviance or coexistence with breast cancer have been reported, increasing the risk of misdiagnosis. Multidisciplinary collaboration not only helps to avoid such errors, but also facilitates earlier preoperative diagnosis and ensures the appropriate use of corticosteroid therapy in selected patients (8,12). Due to the absence of specific clinical or radiological characteristics, imaging findings may be non-specific. Mammography often reveals asymmetric density, while an ultrasound may detect irregular, heterogeneous masses suggestive of abscesses. However, these features are not unique to GM and can mimic other breast pathologies (1).
Although no standardized treatment exists for GM to date, at least to the best of our knowledge, steroids are frequently used to reduce lesion size. However, their use is associated with adverse effects, such as weight gain, hyperglycemia, Cushing syndrome and opportunistic infections (7). Additionally, patient non-adherence can compromise treatment efficacy. Vall et al (3) reported a case in which poor adherence led to multiple recurrences, ultimately necessitating rescue therapy. While the studies by Alvand et al (2) Rajendran et al (10) and Oze et al (4) reported favorable outcomes with conservative management, the lack of long-term follow-up in these cases raises concerns about the sustained efficacy and reliability of conservative treatment strategies.
A previous meta-analysis of 138 cases undergoing surgery and 358 cases with steroid therapy revealed improved outcomes with surgery (complete response: 90.6 vs. 71.8%; recurrence: 6.8% vs. 20.9%) (13). Combining surgery with steroids further improved results, with a 94.5% complete response rate and a 4.0% recurrence rate (13). A conservative approach was initially employed for the patient in the present study; however, recurrence occurred after 1 year. By contrast, wide local excision of the axillary tail achieved a favorable outcome, with no recurrence observed at the one-year follow-up.
The case described herein enriches the existing body of knowledge by elucidating the presentation, complex diagnosis, treatment options and favorable outcomes of GM in accessory breast tissue, guiding clinicians in recognizing and managing this rare condition effectively. However, it is worth mentioning that a longer period of monitoring would strengthen this report and the conclusions drawn significantly.
In conclusion, GM can occur in accessory breast tissue. While corticosteroids may provide favorable short-term results, they do not necessarily prevent recurrence, whereas surgical management may offer more durable long-term outcomes.