Rosai-Dorfman disease (also known as sinus histiocytosis with massive lymphadenopathy) is an uncommon, idiopathic, benign histiocytic lesion. It usually involves the cervical lymph nodes and, less commonly, extranodal sites. Involvement of the breast is rare, with only 17 cases reported in the English literature to date. Here we describe 3 new patients with extranodal Rosai-Dorfman disease in the breast. All 3 patients—aged 45, 53, and 54 years—presented with solid breast lesions that were detected on screening mammography and had no clinical history of Rosai-Dorfman disease or radiographic evidence of extramammary involvement. Initial diagnoses were accomplished by needle core biopsy in the one case and excisional biopsy in the other two. We present the histopathologic findings and follow-up of each patient and conduct a literature review of mammary Rosai-Dorfman disease with emphasis on its differential diagnosis. Because Rosai-Dorfman disease frequently mimics invasive breast carcinoma in its clinical presentation and radiographic appearance—and can mimic other benign or malignant histiocytic lesions microscopically—awareness and appropriate diagnosis of this entity are essential for proper treatment.
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