Extra-nodal Rosai-Dorfman Disease Confined to Breast

Abstract

Abstract Introduction/Objective First described by Rosai and Dorfman in 1969, Rosai-Dorfman Disease (RDD) is an uncommon, idiopathic, reactive lymph node process with an unknown etiology. It may involve extra-nodal organs including the skin, bone, soft tissue, and eyes. However, breast involvement is rare and RDD confined to breast without nodal involvement is extremely uncommon. Methods Here we present a case of RDD confined to breast. The patient was a 51-year-old African American woman who was found to have an irregular, solid left breast mass on routine mammogram, which had speculated irregular margins and measured of 37.0 x 32.0 x 32.0 mm. She did not have any symptoms, nor any palpable lymph nodes. The clinician stated that the lesion was highly suspicious for a breast malignancy and requested a fine needle aspiration (FNA) of the mass, followed by total excision. Results An FNA was interpreted as atypical histiocytic cells in a mixed lymphoid background. Histopathologic examination revealed an ill-defined mass with sheets of histiocytes, plasma cells, and a mixed lymphocytic population, with occasional germinal centers. Some of the histiocytes were spindle shaped and associated with storiform collagen deposition. The histiocytes had single and multiple nuclei and exhibited occasional emperipolesis. Immunohistochemical staining with S100 diffusely highlighted the histiocytes, whereas CD1a was negative. CD3 and CD20 immunostains were positive for mixed-type lymphocytic infiltration. Cytokeratin staining was performed and reassuringly stained only the benign ductal cells. A diagnosis of RDD of the breast was made, based on these histopathologic findings. Conclusion We report an example of an extra-nodal RDD involving the mammary gland that was initially suspected to be breast carcinoma. RDD may still be a diagnostic challenge, especially in a patient with suspected carcinoma. It is the pathologist’s role to lead the clinician to the proper diagnosis and render a correct histopathologic diagnosis.