Idiopathic granulomatous mastitis: a 10-year study from a multicentre clinical database.

Idiopathic granulomatous mastitis (IGM) is an uncommon, chronic inflammatory breast disease with elusive aetiology, simulating malignancy clinically and radiologically. Here we present our 10-year review on a region-wide multicentre IGM database. A retrospective study was performed on a prospectively maintained database from three University affiliated hospitals in Hong Kong and Shenzhen, China. All patients with biopsy proven IGM were included while patients with positive culture of Mycobacterium tuberculosis were excluded. Disease recurrence rate and its prognosticators were evaluated. A total of 102 patients were included between January 2007 and December 2017. Median age was 33 years (range 20-54). Most patients presented with painful inflammatory mass (n = 57); median size at presentation was 37 mm (6-92 mm). Sixty-three patients had bacterial culture performed on the pus sample: eight patients had Corynebacterium kroppenstedtii while four had Corynebacterium species not otherwise specified. Seventy-seven (75.5%) patients received conservative treatment with oral corticosteroid (±antibiotics) and drainage only, while 25 (24.5%) patients received breast lump excision after initial medical treatment. Twelve (11.8%) patients developed recurrence after a median follow-up interval of 14 months (4-51 months). Univariate analysis revealed that abscess on presentation, history of smoking, and presence of C. kroppenstedtii were significant prognosticators for recurrence. Subsequent multivariate analysis with logistic regression revealed cigarette smoking and isolation of C. kroppenstedtii as independent risk factors for disease recurrence (p < 0.05). In conclusion, IGM is uncommon with a recurrence rate of 12%, especially in patients with history of smoking and isolation of C. kroppenstedtii.