Extranodal Rosai-Dorfman Disease of the Male Breast: A Case Report and Literature Review.

Rosai-Dorfman disease (RDD) is a rare histiocytic disorder that most commonly affects lymph nodes but can also present in extranodal sites. Involvement of the male breast is rare and may clinically and radiologically mimic malignancy. A comprehensive review will be valuable for histologic assessment and treatment of similar cases. We report a case of extranodal RDD in a 65-year-old man, who presented with a 48 × 40 × 25 mm left breast mass. The mass was excised with clear surgical margins. Histopathologic examination showed sheets and clusters of large histiocytes with emperipolesis on a background of lymphoplasmacytic inflammation. Immunohistochemistry showed that the lesional cells were positive for S100 and CD68, and negative for CD1a. The morphology and immunohistochemistry confirmed the diagnosis of extranodal RDD limited to the subcutaneous tissue of the breast. The literature review yielded 13 cases of extranodal RDD of the male breast. Four cases lacked sufficient details to be included in the synthesis. All patients presented with unilateral palpable breast masses. Radiologic evaluation was suspicious for malignancy in all 7 patients with imaging reported. Microscopy revealed sheets of large histiocytes with emperipolesis, which were positive for S100 and CD68 and negative for CD1a. No evidence of systemic disease was found. All patients were treated conservatively, with 2 recurrences at 24 months of follow-up. Extranodal RDD of the male breast is exceedingly rare and can mimic carcinoma both clinically and radiologically. Accurate diagnosis requires histologic and immunohistochemical confirmation. Awareness of this entity is critical to avoid overtreatment.