[Extranodal Rosai Dorfman disease (sinus histiocytosis with massive lymphadenopathy). Report of 5 cases].

Sinus histiocytosis with massive lymphadenopathy (SHML) was described in 1969 by Rosai and Dorfman as an benign disorder of the lymph nodes. Involvement of extranodal sites by SHML may occur as part of a generalized disease involving lymph nodes as well as independently of the lymph node status. The clinical course is mostly benign and indolent, but in rare cases the SHML can cause death. We report 5 cases of extranodal Rosai Dorfman disease (ENSHML). The lesions were localized in the soft tissue of the extremities, the head and the skeleton. Histopathological examination revealed a lymphoplasmacellular infiltration and numerous histiocytes with an eosinophilic cytoplasma and vesicular nuclei with basophilic nucleoli. The histiocytes showed emperipolesis with multiple lymphocytes within the cytoplasm and occasionally phagocytosis of other inflammatory cells. The histiocytes were immunohistochemically positive for S 100 protein and macrophage-specific antibodies, but in paraffin material negative for CD1a. We briefly discuss aspects of differential diagnosis of this lesion, too.