Extranodal sinus histiocytosis (Rosai-Dorfman disease) of the brain parenchyma.

Rosai-Dorfman Disease (RDD) is an idiopathic histiocytic proliferation affecting lymph nodes. Although extranodal involvement has been reported in diverse sites, manifestation in the central nervous system (CNS) is extremely rare, particularly in the brain parenchyma. A 39-year-old male presented with an isolated well-circumscribed brain mass in the right temporal lobe, preoperatively thought to be a meningioma. Histology and immunohistochemistry confirmed that the lesion was RDD. The intraparenchymal brain location of RDD appears to have a benign course. Although the adjuvant therapy is a treatment of choice, surgical resection seems to be the appropriate treatment modality. From the clinical point of view RDD might be an important intracerebral entity because it may mimic other lesions, particularly other histiocytic disorders.