Background: The presentation of idiopathic granulomatous mastitis can mimic breast cancer. Therefore, awareness of the condition is important for surgeons. The current series is the largest in a US population. Methods: Retrospective chart review of patients treated at a county, safety-net hospital in Arizona. Cases were identified from January 2006 to January 2019. Sociodemographic information, clinical history, management, and outcomes were collected. Results: There were 145 occurrences of idiopathic granulomatous mastitis among 120 women. Most of the patients (92%) were of Hispanic ethnicity and born outside (87%) of the United States. The average age was 35 years. Nearly all patients (95%) were parous, with an average of 3 pregnancies. Most (88%) presented with a palpable mass, and more than half (54%) of these masses were painful. Six patients had prolactinomas or hyperprolactinemia, 11 patients were pregnant, and 5 were postpartum. Early in the time period studied, 6 patients underwent excision of the masses. The remaining 114 underwent planned observation after biopsy confirmation of the diagnosis. Two patients were lost to follow-up, and the other 112 patients with idiopathic granulomatous mastitis resolved spontaneously. Nineteen had more than 1 episode. Average time to resolution was 5 months (range 0–20). Adjusted log-normal regression analysis found that later age of first live birth was associated with greater time to resolution (P <.01). Conclusion: Idiopathic granulomatous mastitis is a self-limited, benign condition that waxes and wanes and eventually resolves without resection. After diagnosis, medications are unnecessary, and operations can be limited to drainage procedures for fluid collections.
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