Nasal Rosai-Dorfman disease with intracranial involvement: a case report.

Sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman disease) is a rare but distinctive entity. It was initially described as a nodal-based disease but later found to affect a variety of extranodal sites. The diagnosis of Rosai-Dorfman disease is based on the unique histologic changes that are characterized by proliferation of S-100 protein-positive histiocytes, the presence of emperipolesis, and a mixture of prominent lymphoplasmacytic infiltrates. The etiology of Rosai-Dorfman disease is unknown. It usually runs a benign clinic course and may resolve spontaneously, but cases running protracted courses have also been reported. We report an unusual case of recurrent extranodal Rosai-Dorfman disease in nasal and paranasal cavities with intracranial involvement surviving for more than 9 years.