ABSTRACT
<p><b>OBJECTIVE</b>To investigate the diagnosis and differential diagnosis of extranodal Rosai-Dorfman disease.</p><p><b>METHODS</b>Two cases of extranodal Rosai-Dorfman disease were studied using hematoxylin-eosin, and immunohistochemical staining, along with a literature review.</p><p><b>RESULTS</b>The lesions of RDD were characterized by the presence of large histiocytes with emperipolesis, accompanied by infiltration of lymphocytes, plasma cells and other inflammatory cells. The large histiocytes had an abundant cytoplasm, pale to eosinophilic in appearance, positive for S-100 protein staining, with a vesicular nucleus and a small basophilic nucleolus in each cell.</p><p><b>CONCLUSIONS</b>Extranodal Rosai-Dorfman disease is known as an idiopathic proliferative disease of histiocytes with a distinct morphologic feature and is very rare. Differential diagnosis from other types of fibrohistiocytic proliferation lesions is recommended.</p>