The effect of methotrexate monotherapy on treatment-resistant idiopathic granulomatous mastitis patients.

Background: Idiopathic granulomatous mastitis (IGM) is a disease of unknown etiology, involving a chronic inflammatory process, characterized by noncaseating granuloma formation. IGM can mimic a tumor clinically and radiologically. Since we are a tertiary referral center, most of our patients (n = 56, 87.5%) are secondary admissions who have previously had antibiotics and steroid treatments; therefore, we accept these patients as resistant cases. Here, we aim to present our single-center series of 64 patients with resistant IGM who underwent methotrexate monotherapy. To the best of our knowledge, our study includes the highest number of patients described in the literature with IGM who have undergone this treatment.

Methods: This study included 64 patients, 56 of which were resistant cases, diagnosed with IGM between January 2013 and January 2020 at Istanbul University Cerrahpasa, Cerrahpasa Medical Faculty, General Surgery Breast Outpatient Clinic that were followed-up at least once. These patients were administered oral methotrexate monotherapy 15 mg/week for 24 weeks, and in relapsed cases, the treatment was up to 20 mg/week for 1 year. Folic acid 10 mg/week was given as a supplement to all patients.

Results: Complete recovery was observed in 52 (81.25%) of the 64 patients. Follow-up was discontinued by 4 patients. The dose was increased and the duration of treatment was extended up to 1 year when relapse was observed in 8 patients and complete response was then obtained in these cases. Only 3 patients (4.69%) experienced side effects and were switched to subcutaneous treatment due to nausea.

Conclusion: Considering the high patient compliance, low recurrence, minimal side effects, and overall success of the treatment, we believe that methotrexate monotherapy may be used in treatment-resistant IGM patients and may also be the first choice for first-line treatment in the future.