title: Extranodal (dural) Rosai-Dorfman disease radiologically and histologically mimicking meningioma: a case report.
abstract: BACKGROUND
  Rosai-Dorfman disease (sinus histiocytosis with massive lymphadenopathy) is an idiopathic nonneoplastic lymphohistiocytic proliferation with variable clinical presentations, sometimes mimicking other disorders including neoplasm. Particularly, intracranial Rosai-Dorfman disease is rare and without well-established optimal treatment modalities.
  
  
  METHODS
  A 42-year-old man presented with gradually progressive unilateral hearing and vision loss over a two-year period. An MRI of the head showed findings consistent with meningiomatosis. He subsequently underwent a dural biopsy, and histologic examination of the lesion showed sheets of histiocytes positivefor CD68 and S-100 and negative for CD1a within a rich lymphoplasmacytic infiltrate. Some of the histiocytes showed emperipolesis of lymphocytes and plasma cells. These findings were consistent with Rosai-Dorfman disease. Interestingly, EMA-positive meningothelial whorls were seen scattered within the dominantly histiocytic-appearing process, mimicking the appearance of meningioma; these whorls were thought to be reactive in nature.
  
  
  CONCLUSIONS
  This case is important as it high-lights unusual clinical and histopathologic features of Rosai-Dorfman disease, thereby adding to the spectrum of manifestations of this entity. Awareness of such features is helpful in averting the misdiagnosis of intracranial Rosai-Dorfman disease with reactive meningothelial hyperplasia as meningiomas.
authors.forename: Samer
authors.initials: S
authors.lastname: Nassif
authors.forename: Fouad
authors.initials: F
authors.lastname: Boulos
mesh_terms: D000328:Adult; D003937:Diagnosis, Differential; D004388:Dura Mater / Q000473:pathology*; D015618:Histiocytosis, Sinus / Q000175:diagnosis*; D006801:Humans; D008297:Male; D008577:Meningeal Neoplasms / Q000175:diagnosis*; D008579:Meningioma / Q000175:diagnosis*