Idiopathic Granulomatous Mastitis: Imaging Findings and Outcomes with Nonsteroidal Treatment in a Predominantly Hispanic Population.

Objective: We describe the demographics, clinical presentation, imaging findings, and treatment response among 235 cases of biopsy-proven idiopathic granulomatous mastitis (IGM) at a single institution.

Methods: An institutional review board-approved retrospective search of the breast imaging database was performed to select patients with biopsy-proven IGM between 2017 and 2022. Retrospective review evaluated clinical presentation, imaging findings with US and mammography, and treatment recommendations (antibiotics, nonsteroidal anti-inflammatory drugs [NSAIDs], warm compresses, or observation only). Response to treatment was evaluated on follow-up US. A favorable treatment response was a decrease in size or resolution of disease on follow-up imaging. Statistical analysis using Poisson regression was performed to evaluate the clinical outcomes associated with each treatment.

Results: A total of 235 patients met the selection criteria with a mean age of 38 years (18 to 68). The majority of patients were Hispanic (95%, 223/235). Of all patients, 75.3% (177/235) received treatment (consisting of 1 or any combination of antibiotics, NSAIDs, warm compresses), 24.7% (58/235) were treated with observation, 78.7% (185/235) returned for follow-up imaging, and 21.3% (50/235) were lost to follow-up. Of those with follow-up imaging, disease improvement was seen in 70.3% (102/145) of patients who received treatment compared with 72.5% (29/40) of patients treated by observation alone. Multivariate analysis further showed no difference in clinical outcomes among the treatment of unifocal, multifocal, or recurrent IGM.

Conclusion: Nonsteroidal treatment of IGM showed no significant improvement on follow-up imaging compared to treatment with observation alone in a predominantly Hispanic patient population.