Background: Idiopathic granulomatous mastitis is a granulomatous mastitis without any other attributing causes. Although the disease is rare in the world, but it seems Iran has higher prevalence. A few comprehensive studies have been performed on etiological features and risk factors of idiopathic granulomatous mastitis in Iran. We aimed to present a good epidemiological and etiological feature of breast granulomatous diseases in our country in a multi-center study.

Methods: In this case series study,115 recorded documents with final diagnosis of granulomatous mastitis from September 2009 to August 2014 were assessed. All patients’ sample slides were stained specifically with Gram, PAS, and acid fast staining methods. Also, for assessing the presence of the genome of M.tuberculosis, the PCR technique was applied. At the same time, all patients filled out questionnaires containing basic information, possible underlying causes, early symptoms and treatment.

Results: One hundred and fifty registered patients, 3(2/6%) patients with a diagnosis of secondary granulomatous inflammation and 112 (97/4%) patients diagnosed as idiopathic granulomatous inflammation were observed in the 5-year period. All patients with diagnosis of idiopathic granulomatous mastitis were married with history of pregnancy and all except for one had experience of breastfeeding.

Conclusion: The presence of 112 patients in a 5-years period in three hospitals confirmed the higher prevalence of Idiopathic granulomatous mastitis in Iranian women in reproductive ages. With regard to presence of fertility and lactation in nearly all patients, the etiologic role of these factors is highlighted. Despite using different regimens in treating in our study, relapse rate was reported as 9%.