A Rare Case of Isolated Intracranial Rosai-Dorfman Disease Mimicking Optic Nerve Meningioma: A Case Report and Literature Review.

Sinus histiocytosis with massive lymphadenopathy, or Rosai-Dorfman disease (RDD), was first described in 1969 as a reactive condition of unknown etiology that is characterized by a proliferation of histiocytes exhibiting emperipolesis of both lymphocytes and plasma cells. It usually presents with painless cervical lymphadenopathy either with or without extranodal manifestations. Intracranial involvement of this disease is extremely rare. Intracranial RDD occurs in <5% of all patients with extranodal disease. Here, we report a case of RDD with isolated intracranial involvement. A 67-year-old male presented with a long-standing headache, retro-ocular pain, and progressive visual loss of the left eye. Magnetic resonance imaging showed features of optic nerve meningioma. The histopathology revealed sheets of histiocytes displaying emperipolesis. These histiocytes were S100 positive; however, a CD1a and epithelial membrane antigen were negative.