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Breast Imaging

E1176. The Other Mastitis: Imaging, Diagnosis, and Treatment of Granulomatous Mastitis

Singh A,  Gupta E,  McElligott S. Northwell Health, New Hyde Park, United States

Address correspondence to A. Singh (asingh589@gmail.com)

Background Information: Granulomatous mastitis (GM) is a rare and benign inflammatory disease of the breast that can clinically mimic breast cancer or other infections. The disease mostly affects women of childbearing age or women with a history of oral contraceptive use and usually develops within 6 years after pregnancy. Histologically, there are nonnecrotizing granulomas confined to breast lobules, with no evidence of microorganisms. We will describe the mammographic (MG), ultrasound (US) and MR features of GM and its potential mimics.

Educational Goals/Teaching Points: The goals of this exhibit are to review the epidemiology and clinical presentation and discuss the key pathologic features of GM using MG, US, and MR findings with relevant cases. Additionally, we will review imaging mimics seen at our institution, including breast carcinoma, infectious mastitis, hidradenitis suppurativa, and other benign inflammatory conditions of the breast, and the distinguishing features, and discuss management.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: MG features can be variable and nonspecific, ranging from normal findings in patients with dense breasts to multiple masses with benign or malignant features, to a large focal asymmetry. Calcifications are rare. Abnormal lymph nodes or skin thickening were identified in 20% of cases. US appearance of multiple grouped and contiguous tubular hypoechoic lesions, including sinus tracts to the skin, and a dominant hypoechoic mass should suggest GM in the appropriate clinical setting. Common appearance on MRI is focal or diffuse asymmetric signal intensity changes (T1 hypointense and T2 hyperintense) without significant mass effect; however, masses and abscesses can also be seen. Involvement can be unilateral and diffuse or confined to the periphery in one quadrant of the breast. The MRI appearance and kinetics are nonspecific and cannot definitively distinguish between GM and carcinoma.

Conclusion: GM is a rare inflammatory condition (although not uncommon in some practice settings). It has clinical and radiologic findings similar to those of breast cancer. Core biopsy is required for definitive diagnosis. The histology findings on core biopsy, with the exclusion of other granulomatous diseases including sarcoidosis and TB, are typically diagnostic. The optimal treatment of GM remains controversial. Once the diagnosis is established by tissue sampling, wide local excision and corticosteroids are the first line of treatment. Radiologists need to be familiar with the imaging appearance of GM and its treatment to make the appropriate diagnosis and to guide management as many of these patients are frequently refractory to treatment and require long-term follow-up.