Fine needle aspiration cytology and immunocytochemical characterization of the histiocytes in sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman syndrome).

A fine needle aspiration (FNA) biopsy of an enlarged lymph node in a three-year-old boy who had asymptomatic cervical and submandibular lymphadenopathy showed large histiocytes with abundant pale, eosinophilic cytoplasm containing well-preserved lymphocytes and occasional plasma cells and granulocytes. These features were consistent with a diagnosis of sinus histiocytosis with massive lymphadenopathy (SHML). Immunophenotypic study of the histiocytes, performed on the FNA smears and on paraffin-embedded sections, showed reactivity for S-100 protein and alpha-1-antichymotrypsin and negativity for lysozyme. These features, which are characteristic of SHML, demonstrate the reliability of FNA cytology in making the diagnosis of this disorder.