Clinical, histological features, and predictors of relapse in patients with idiopathic granulomatous mastitis.

Idiopathic granulomatous mastitis is a benign, inflammatory disease of breasts characterized by non-caseating granulomas. Our study aims to identify distinguishing clinical and histopathological features of relapsing disease compared to those in complete remission. We queried databases at our institution (1990-2021) to include females ≥18 years with biopsy-proven diagnosis of idiopathic granulomatous mastitis, excluding patients with breast cancer, lymphoproliferative disorders, solid organ malignancy, foreign body reaction in breast, plasma cell mastitis, and ductal ectasia. Remission was defined as a 3-month period without recurrence of symptoms or imaging findings. Relapse was defined as recurrence after 3 months of remission. Clinical and histopathological features were compared using 2-sample t tests and chi-squared tests. Of the 27 patients that met our inclusion criteria, the mean age at diagnosis was 35.8 years (± standard deviation 9.4 years) with a mean body mass index of 31.7 kg/m2 (± standard deviation 6.7 kg/m2). 11 (41%) were Hispanic, 25 (93%) had at least one previous full-term pregnancy prior to diagnosis and 8 (30%) were on oral contraceptives. Remission was seen in 18 patients (66%) and 9 (33%) had relapse. Six of these patients received steroids after antibiotics, while 5 patients received methotrexate. Three (33%) patients with relapse and 14 (77%) with remission, had abscess formation confirmed on histopathology (P = .04). Patients with remission had a higher number of abscesses on histopathology and history of oral contraceptive use was associated with more relapse. By identifying key clinical and histopathological findings in this population may guide prognosis and treatment of these patients.