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Breast Imaging

E2464. Quarantine! Granulomatous Mastitis of the Breast

Koethe Y,  Hayward J,  Carpentier B. University of California, San Francisco, San Francisco, CA

Address correspondence to Y. Koethe (yilun.koethe@ucsf.edu)

Background Information: Granulomatous mastitis (GM) is a clinical, radiologic and pathologic entity, which may occur due to infectious or systemic granulomatous disease. When other causes are excluded, a diagnosis of idiopathic granulomatous mastitis (IGM) is made. Clinical and imaging presentations may mimic infection or malignancy, making its diagnosis and management challenging.

Educational Goals/Teaching Points: The diagnosis and management of GM require multidisciplinary collaboration between some combination of the primary care physician, radiologist, pathologist, surgeon, and rheumatologist. This educational exhibit reviews nine cases of GM in our practice to illustrate the clinical and imaging findings at different stages. At the completion of this exhibit, the radiologist will make the diagnosis of GM using imaging, clinical, laboratory, and histopathologic findings. Additionally, the expected imaging and clinical course for this disease will be reviewed.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: GM is divided into two subtypes, specific and idiopathic. Specific GM is due to a local inflammatory response (for example, infection or foreign body) or a systemic inflammatory response (for example, sarcoidosis or granulomatous polyangiitis). IGM is a diagnosis of exclusion. Clinically, both subtypes can mimic breast cancer or abscess. Unlike typical mastitis and abscess, GM does not respond to antimicrobials, persists despite surgical drainage, recurs often, and frequently involves both breasts. On mammography, it may present as a focal asymmetry or mass. Ultrasound is more sensitive and may demonstrate a heterogeneous mass or fluid collection. Tissue sampling is required for diagnosis and to exclude malignancy. To differentiate specific GM from IGM, laboratory and clinical history (such as tuberculosis or rheumatoid arthritis) will play a critical role. This exhibit reviews the clinical and radiologic evolution of GM throughout its many stages.

Conclusion: Radiologists play an integral role in the initial diagnosis and follow-up of GM. Understanding the clinical, radiologic, and pathologic characteristics will inform appropriate diagnosis and management of this disease.