Idiopathic Granulomatous mastitis: Clinical characteristics, treatment and outcome in 380 patients: IGM - diagnostics and treatment approach

Background: Idiopathic Granulomatous Mastitis (IGM) is a chronic inflammatory disease of the breast. Although most of the studies have reported IGM as a rare disease, recent studies have shown an increase in the prevalence, especially in developing countries. The most important challenge is about the appropriate treatment of this disease that is not established yet. The aim of this cross-sectional study was to review the definite cases of IGM in terms of clinical characteristics and the result of treatment at Motamed Cancer Institute (MCI). Methods and Materials: This retrospective study was conducted on 383 women who were referred to Motamed Cancer Research Institute with a confirmed diagnosis of IGM for a two-year period from March 2015 to February 2018. The demographic and clinical characteristics and the result of treatment options were extracted from the patients’ medical records. The data was statistically analyzed using SPSS version 22. Results: Among 383 pathologically proven cases with IGM, the mean age was 35.6+7.593 years, 97% of them had a history of pregnancy and 95.2% had breastfed. The most common symptoms of the disease were palpable mass, pain, fistula to the skin and inflammation respectively. In response to the prescribed treatments, among 241 patients with available follow-up, the most commonly used treatment was Corticosteroids + Methotrexate (70.1%), the highest complete remission was in the group receiving Corticosteroid (100%) and Methotrexate (97%) respectively and the highest partial remission belonged to Corticosteroid+ Methotrexate with the frequency of 21.3%. The shortest time to complete remission belonged to Methotrexate regimen with a mean duration of 5.83 months and the highest recurrence rate was seen in the group receiving Corticosteroids alone (16.7%). Conclusion: According to the results of this study, among the prescribed treatments, the highest rate of complete remission with the lowest duration and recurrence rate belongs to Methotrexate regimen. Corticosteroids were associated with the high rate of complete remission but high rate of recurrence yet. Given the autoimmune nature of IGM, such results seem expectable and Methotrexate could be recommended especially in moderate to severe forms and as an additional treatment to taper Corticosteroids. Implementation of clinical trials regarding the best treatment options for IGM is recommended.