Fine needle aspiration cytologic findings in a case of sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman syndrome)

The clinical, fine needle aspiration (FNA) cytologic and histologic findings in a case of sinus histiocytosis with massive lymphadenopathy (SHML) in a five-year-old boy are presented. The FNA smears showed a proliferation of plasma cells, lymphoid cells and histiocytes demonstrating emperipolesis that is characteristic of this benign disorder; these cytologic findings were reported as a reactive lymphoid infiltrate with a high content of benign histiocytes. The diagnosis was made on a subsequent open biopsy performed on the persistent lymphadenopathy. The differential diagnosis of lymph nodes containing a prominent component of histiocytes is discussed.