Extranodal (dural) Rosai-Dorfman disease radiologically and histologically mimicking meningioma: A case report

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 wellestablished optimal treatment modalities. Case: A 42-year-old man presented with gradually progressive unilateral hearing and vision loss over a twoyear 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 positive for 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. Conclusion: This case is important as it highlights 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.