Isolated intracranial rosai-dorfman disease involving the meninges: report of a rare case.

Sinus histiocytosis with massive lymphadenopathy or Rosai-Dorfman disease (RDD) is a reactive condition of unknown etiology, characterised by a proliferation of histiocytes exhibiting emperipolesis of lymphocytes and plasma cells. It usually presents as bilateral painless cervical lymphadenopathy. Extranodal RDD without nodal disease is seen in 23% of the cases. Intracranial RDD occurs in less than 5% of the total number of patients with extranodal disease. Isolated intracranial RDD in the absence of nodal disease is exceptional. We report a case of Rosai-Dorfman disease with isolated intracranial involvement. A 38-year-old man came with long-standing headache and the magnetic resonance imaging (MRI) scan showed features of meningioma. The histopathology revealed sheets of histiocytes displaying emperipolesis. These histiocytes were S100 positive but CD1a and epithelial membrane antigen negative.