Evaluating the efficacy of topical steroids in idiopathic granulomatous mastitis: a prospective cohort study

Oral steroids are recommended as the first-line treatment for idiopathic granulomatous mastitis (IGM), but frequently induce significant side effects. Topical steroid therapy has recently emerged as a potential alternative for IGM, however current evidence regarding the efficacy of topical steroids remains scarce, primarily derived from small case series and retrospective reports. This prospective, observational cohort study evaluated the outcomes of patients with IGM treated with topical steroids.

From January 2022 to October 2024, 76 patients diagnosed with IGM and treated with topical steroid therapy at West China Hospital were prospectively included in the study. Inclusion criteria comprised adult females with histologically confirmed IGM who were treatment-naive. At baseline, we recorded demographic data, clinical manifestations, as well as lesion size and location. Clinical evaluations incorporating both physical examination (PE) and ultrasonographic findings were performed biweekly to assess treatment response. Primary outcomes included symptom resolution, lesion size reduction, recurrence rates, and treatment-related adverse events. Follow-up was conducted at 1, 3, and 6 months, and every 6 months thereafter.

The median age at IGM diagnosis was 33.2 years. Clinical presentations included unilateral breast masses in nearly all cases (97.5%), with 75% of lesions measuring 2-5 cm in diameter. Breast pain was reported by 67.1% of patients; 64.3% (45/70) of patients responded to topical steroid therapy, with a complete remission (CR) rate of 32.9%. The median time to CR was 60 days. The presence of a breast abscess was associated with significantly reduced response to the treatment (P=0.009). During a median follow-up of 63 days, only 4 patients (8.9%) experienced recurrence. Adverse effects were limited to local issues (e.g., erythema, skin atrophy) with no systemic side effects reported.

Topical steroids represent a feasible alternative to oral steroids for select IGM patients, particularly due to their reduced risk of systemic adverse effects. When a breast abscess develops, other intervention should be undertaken promptly.