Granulomatous mastitis (GM; also known as granulomatous lobular mastitis or granulomatous lobulitis) is a rare and benign condition of the breast. GM was initially described by Kessler and Wolloch 1 in 1972 as a condition unassociated with trauma or infection. The etiology of GM is unknown, although an autoimmune component is suspected. 2,3 It typically affects women of childbearing age and is commonly associated with pregnancy, breastfeeding, and oral contraceptive use. 4 The symptoms of GM tend to overlap with more malicious entities, particularly breast carcinoma. However, it may also be asymptomatic. The imaging characteristics of GM are variable and likewise tend to overlap with those of breast carcinoma. GM can be occult by mammography, but the entity is rarely occult as detected on sonography. 5 The sonographic findings are varied but can be suggestive of the entity. GM is commonly diagnosed by tissue sampling under ultrasound guidance. Proper identification and diagnosis of GM is important to prevent misdiagnosis and/or delayed treatment. Treatment protocols and treatment efficacies vary, and the condition is often chronic.