Abstract: Rosai-Dorfman disease (also called sinus histiocytosis with massive lymphadenopathy) involves lymph nodes or lymph nodes with extranodal sites. We present a unique case of a patient presenting with a breast mass and axillary lymphadenopathy, mimicking malignancy clinically and radiographically. Core needle biopsies of the breast and axillary lymph node showed histologic features concerning the lymphoma. However, excisional biopsy specimen demonstrated characteristic features of Rosai-Dorfman disease. The disease recurred locally 6 months later in the same breast, 1 month later in the contralateral breast, and 11 month later in the subcutaneous tissue of left flank. A review of the literature of Rosai-Dorfman disease involving the breast is also presented.