Background/Purpose: Granulomatous Mastitis is a rare, inflammatory disease of the breast. Presenting symptoms in the breast can be unilateral or bilateral pain, masses, skin induration, erythema, discharge, and abscess formation. Few patients experience self-limited disease over 1-2 years, while most have a longer relapsing course. Imaging modalities such as mammography, ultrasonography, and magnetic resonance imaging (MRI) help characterize lesions, but definitive diagnosis requires histologic examination of tissue via biopsy. Frequently used treatment modalities include antibiotics, prednisone, and surgery, which are often ineffective and fraught with recurrence rates of 50%. This study describes the largest granulomatous mastitis cohort to date in the Americas and Europe with an emphasis on the efficacy of methotrexate treatment.

Methods: Institutional Review Board (IRB) approval was obtained from Stanford University. The Stanford Translational Research Integrated Database Environment (STRIDE) was queried using the terms “granulomatous mastitis” and “rheumatology” and “methotrexate” or “prednisone” from 2006-2017. Inclusion criteria included histopathologically-established granulomatous mastitis patients who were evaluated, treated with methotrexate, and had at least one follow up appointment at the Stanford Immunology and Rheumatology Clinic. Retrospective chart review was performed including pertinent demographic, medical, clinical, and treatment information.

Results: Of the 70 patients identified using STRIDE, 19 met the inclusion criteria. All patients were female with an average age of 33.5 years at the time of presentation. Majority were Hispanic (57.9%), followed by Asian (21.1%), African American (10.5%), and Caucasian (10.5%). The average parity at presentation was 2 children with a latency between the last pregnancy and diagnosis of 29.4 months. Presenting symptoms were unilateral in 68.4% of patients and included breast pain/tenderness (68.4%), mass/lump (47.3%), swelling (21.1%), erythema (21.1%) and induration (15.8%). Most patients had prior unsuccessful treatments with antibiotics (84.2%), incision and drainage (42.1%), prednisone (36.8%), and surgical intervention (5.3%). After three and six months of methotrexate treatment, 89.5% and 94.4% of patients noted disease improvement, respectively. In patients who were compliant with prescribed methotrexate treatment for 12-15 months, 71% achieved disease remission and were disease free on follow up ranging from 1-5 years. The average methotrexate dose in the first 12 months of treatment was 18mg PO weekly. The most common reason for termination of treatment was disease remission.

Conclusion: Our center’s experience demonstrates that granulomatous mastitis presents predominately in multiparous Hispanic females of childbearing age as unilateral, painful breast masses. Methotrexate is an effective treatment modality resulting in sustained disease remission in most patients who are compliant with therapy for at least one year.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/methotrexate-in-the-treatment-of-granulomatous-mastitis-a-retrospective-review-of-19-cases/