Autoimmunity, hormonal disorders and infection are among the most likely factors in the etiology of IGM. The most widely accepted hypothesis is that IGM develops as a result of an autoimmune process [2, 11, 12]. The results of our study support this hypothesis. The disease developed in the passive breast in more than 90% of our patients with a passive breast history. When breastfeeding in a lactating breast does not occur, ductal epithelium damage occurs because of milk stasis. Extravasation of secretions, as a result of ductal damage, cause macrophage and leukocyte migration into the tissue, triggering local inflammation [13–16]. Based on this information and our observations, we consider that ductal damage plays an important role in the pathogenesis of IGM, and that inflammation resulting from ductal damage due to any reason may lead to IGM.
On the assumption that the disease mechanism in IGM was autoimmune, steroid and other immunosuppressive agents have been used in its treatment and the disease was demonstrated to respond to these agents [11, 12]. However, common side effects, including myopathy, iatrogenic Cushing syndrome, hypertension, weight gain and hyperglycemia, may occur with systemic steroid use [17, 18]. These side effects may have a severe effect on quality of life and result in the patient requiring long-term treatment. Although the use of medical treatments for suspicious etiological factors, especially autoimmunity, is widespread, surgery is still a common treatment method. However, surgical applications can cause poor cosmetic outcomes, and recurrence rates after surgery are considerably higher, as in our study. In the treatment of benign diseases, the development of side effects that reduce the quality of life or result in poor cosmesis are undesirable. However, the possibility of experiencing these side effects after LST is negligible, in our experience.
The response of all lesions to steroid injection in our patients supports the hypothesis that IGM develops due to an autoimmune process. Özel et al. [19] found positivity in rheumatoid factor in 6 of 8 patients, and anti-nuclear antibody and antiDs DNA antibodies in 2 of 8 patients with a diagnosis of IGM. In another study, Saydam et al. [20] reported a difference in serum interleukin 22 and interleukin 23 levels in patients with (n = 26) and without (n = 15) a diagnosis of IGM, and stated that this difference supports an autoimmune etiology for IGM. However, data on this aspect of IGM are limited and further studies are needed on the presence of autoimmune markers in IGM.
The proportion of patients in whom a complete recovery was achieved following LST was gratifying, given that the optimal treatment for IGM is controversial. In addition, the findings in patients exhibiting partial recovery that the lesion size did not increase and the disease did not progress may be an indication that the steroid restricts the disease by suppressing active inflammation. In a similar study, Toktaş et al. [10] reported that 93.5% of the patients undergoing LST responded to the treatment. These results show that LST is an effective method in the treatment of IGM.
In the LST Group, the presence of a lesion ≥ 3 cm in size, fistula or abscess made treatment less effective and patients with these features generally required a greater NoS for successful treatment. In patients with a fistula, the treating physician was able to observe injected steroid leaking directly into the fistula, thus reducing the concentration in the lesion. In addition, in patients with an abscess, re-formation of abscess negatively affected the treatment process. In earlier studies classifying IGM, the disease was considered to be complicated in the presence of fistula and abscess [21–23]. The results of our study also support this view. In addition, our detailed size analysis showed that a lesion size of ≥ 3 cm prolonged the treatment process, and we suggest that lesions of these sizes should also be considered as complicating the disease.
One of the common symptoms of IGM is pain [1, 11]. To the best of our knowledge, our study is the first study evaluating pain intensity in IGM. The NPRS we used for this purpose is a sensitive and convenient tool in practice and has previously been used in many studies with high reliability [24]. More than 75% of our patients described their pain as severe before treatment, which highlighted the importance of pain relief as part of IGM treatment. Following the first LST session, reported pain regressed from severe to mild and reached tolerable levels soon after the first session in most patients. After completion of treatment, complete pain relief was reported by most, and no patient describing her pain as severe, suggesting that LST is very successful for pain management in IGM. Since the pain of most patients regressed to moderate and some continued to describe their pain as severe in surgical treatment, it can be concluded that LST is superior to surgery in pain management.
Steroids are known to have a wide range of side effects. However, intralesional and topical application, as used in the LST group, was found to be safe with no evident side effects. In contrast, Çetin et al. [25] reported local side effects in the breast skin in 24.4% and systemic side effects in 2.4% of patients due to usage of topical steroids. In addition, 38.2% of patients developed systemic side effects, such as hirsutism, weight gain and iatrogenic Cushing syndrome related to systemic steroid use. Toktaş et al. [10] also reported local side effects at a rate of 2.2% in their LST group, and systemic side effects at a rate of 9.4% in the group treated with systemic steroids. It is notable that systemic treatment was not reported to be superior to local applications in terms of treatment efficacy in either of these studies. As a result, we suggest that local applications of steroids should be used in the treatment of IGM, as localized side effects can be easily managed when compared to side effects from systemic treatment.
Recurrence rates after surgical treatment are high in IGM, with rates in the literature generally reported to be between 5% and 50% [1, 11, 13, 26] although the highest recurrence rate after surgery was 72.7% [27]. We suggest that local excision should be avoided in the treatment of IGM, since 83.3% of patients with local excision had recurrence in our study. Occurrence of relapse in patients undergoing wide excision with apparent negative margins may be an indication that the inflammation had affected more tissue than could be detected. In contrast, the absence of recurrence in LST may indicate that the steroid suppresses active inflammation completely. Moreover, resection in IGM can cause undesired cosmetic results [8, 10, 28]. Due to high recurrence rates and poor cosmetic results, patients may require multiple operations and some of these patients even require mastectomy [29]. These cosmetic problems also lead to psychological problems [29, 30]. The probability of cosmetic problems in LST is relatively lower.
Our study has several limitations. First, it is a retrospective study with a limited number of patients. Second, the follow-up period was insufficient in terms of recurrence risk. Third, there is a scarcity of data in the literature concerning LST and no defined treatment protocol is recommended. Therefore there is a requirement for long-term follow-up studies involving larger patient groups, which would yield more data about treatment efficiency and recurrence rates following LST. These studies could also help to identify the optimal protocol for LST.