Background: Idiopathic granulomatous mastitis (IGM) is a rare, benign, chronic inflammatory condition of the breast that can mimic inflammatory breast cancer and periductal mastitis (PDM). Eighteen patients with a histopathologic diagnosis of IGM, seen over a period of 25 years, were retrospectively reviewed and compared with 133 patients with PDM and 100 normal patients.
Study design: The unit's pathology database and clinic letters for this time period were used to identify patients who had presented with IGM. A retrospective review of the notes was used to extract reproductive factors, cigarette smoking habits, and ethnicities that were recorded at presentation. These were compared with data from a similar group of patients with PDM and a control group.
Results: All IGM patients were women. Median age was 36 years (range 18 to 67 years) compared with 52 years (range 20 to 77 years) for PDM patients (p < 0.001). Seventeen percent of IGM patients were smokers at the time of presentation, as compared with 60% of PDM patients (p < 0.001). Although parity was similar for all groups, 10 IGM patients (56%) had given birth in the last 5 years, compared with 6 (5%) PDM patients (p < 0.001) and 20 (20%) in the control group (p=0.0194). Two IGM patients had recurrences after pregnancy. The course of IGM varied from 11 to 105 weeks and was not affected by any treatment modalities.
Conclusions: IGM patients are younger, have given birth more recently, and are less likely to be Caucasian as compared with PDM patients. IGM is not related to smoking and can recur. Treatment should be supportive.