Rosai-Dorfman Disease of the Breast: Radiologic-Pathologic Correlation.

Rosai-Dorfman disease (RDD) is a rare non-Langerhans cell histiocytosis characterized by the accumulation of histiocytes, primarily in the lymph nodes but also in extranodal sites, including the breast. Rosai-Dorfman disease is infrequently found in the breast, and limited literature exists on its imaging presentation. About two-thirds of cases present as a palpable mass and one-third as a finding on screening mammography. On mammography, the majority are masses with oval shape and indistinct margins. Almost all US findings are masses, and the majority have an irregular shape and indistinct margins. Treatment of RDD involving the breast varies and is tailored to its presentation and extent of involvement. About two-thirds of cases are limited to the breast, and spontaneous resolution often occurs. Most are treated conservatively without medical or surgical intervention. Alternatively, cases with single-site or skin-only involvement of the breast may undergo surgical excision for definitive treatment. FDG PET/CT is typically used at initial diagnosis for staging and subsequently for disease surveillance. Disseminated disease may require chemotherapy, radiation therapy, and immunomodulatory therapy. Although it is rare, breast imaging radiologists should be familiar with the imaging presentation of RDD because initial diagnosis may be made with breast biopsy. Referral to hematology oncology or a multidisciplinary team is important for further management because treatments vary based on disease location and extent.