Breast involvement by extranodal Rosai-Dorfman disease: report of seven cases.

Seven cases of breast involvement by extranodal Rosai-Dorfman disease are presented. The patients were women and their ages ranged from 15 to 84 years. Three patients had disease confined to the breast; one had involvement of the breast and ipsilateral axillary lymph nodes, and two had bilateral breast involvement as well as disseminated systemic disease. In all cases the clinical and radiographic presentation of the breast lesion raised the possibility of a malignant tumor. All but one of the lesions were treated by excisional biopsy. Microscopically, the lesions were relatively circumscribed, often multinodular masses, located in the breast stroma, with or without associated involvement of the subcutaneous tissue and dermis. They were composed of sheets of S-100 protein-positive large histiocytes displaying lymphocytophagocytosis, scattered in a polymorphous background of mature lymphocytes and plasma cells. The microscopic differential diagnosis includes idiopathic granulomatous mastitis, infective granulomas, Langerhans' cell histiocytosis, Erdheim-Chester disease, fibrous histiocytoma, and malignant melanoma.