[Primary central nervous system lymphomatoid granulomatosis: a case report].

Lymphomatoid granulomatosis (LYG) is a rare Epstein-Barr virus-associated multisystem lymphoproliferative and granulomatous disease histologically characterized by angiocentric and angiodestructive cellular infiltrate. LYG usually involves the lungs, skin, kidneys and brain, but isolated central nervous system LYG has been reported rarely. We describe a 57-year-old man with histologically proved LYG confined to the brain. The patient complained of visual disturbance, and was admitted to our hospital. Gadolinium-enhanced T1-weighted MRI showed irregular, partly cystic and lobulated enhancement in the left occipital lobe, suggesting the presence of possible neoplastic lesions such as glioma, malignant lymphoma or metastatic brain tumor. We performed surgical resection of the lesion. Histological and immunohistochemical examinations of the tumor showed angiocentric polymorphic infiltration and granulomatous reaction, consisting of CD3-positive small lymphocytes and CD20-positive large atypical cells. Subsequently, in situ hybridization study for EBER (Epstein-Barr virus encoded small RNA) was performed and proved that the large atypical cells were positive for EBER. These findings were compatible with LYG. We emphasize that the possibility of LYG should be considered in the differential diagnosis of any ring-like enhancing mass lesions on MR images, though less specific for LYG. Histopathological examination is indispensable for the final diagnosis and the choice of an optimal treatment strategy.