Idiopathic Granulomatous Mastitis; Radio-pathologic Findings and Grading Based on Clinical Presentation and Treatment Outcome in 224 Patients

Idiopathic granulomatous mastitis (IGM) is a rare inflammatory disease of the breast with unknown etiology. Clinico-radiologic findings can mimic breast cancer. Further pathologic evaluation to rule out malignancy is mandatory. Recognizing the severity of the disease is crucial to choosing the most effective therapeutic modality. The aim of this study is to evaluate clinical and radio-pathologic features of IGM, and the treatment outcome in a large series of IGM patients in Iran.

The retrospective charts of 243 patients suspicious of IGM, between December 2007 and September 2017 were reviewed. Patients with confirmed diagnosis of IGM were classified into four grades of severity. Demographic information, clinical and radio-pathologic findings, severity and treatment outcomes were collected.

Overall, 224 patients were confirmed to have IGM. Breast mass and erythema were the most common clinical findings. Mammographic findings mimicked malignancy in 34%. Lobulo-centric non-caseating granulomas were the most common pathologic finding. Also, 61.5% of the patients had mild to moderate symptoms and 49.5% of them recovered completely by observation. In addition, 53 (25.9%) patients had severe symptoms and 30.8% of them were resistant to treatment.

IGM is a diagnostic challenge. Its diagnosis is based on exclusion and a close cooperation between the clinician, the radiologist and the pathologist. Mild to moderate cases can be managed conservatively; however, severe cases may need further aggressive medical or surgical treatments.