Lymphoplasmacyte-rich meningioma: a convexity mass with regional enhancement in the adjacent brain parenchyma.

Lymphoplasmacyte-rich meningioma (LPM) is a rare, benign variant of meningioma, characterized by massive inflammatory cell infiltration and a variable proportion of meningothelial tumorous elements. Here we report the clinicopathological features of an LPM located at the right frontal convexity in a 37-year-old woman. The patient had suffered an initial generalized tonic-clonic seizure when she was 32 weeks pregnant. The lesion exhibited low intensity on T1-weighted MRI and high intensity on T2-weighted images, with surrounding parenchymal edema. The mass exhibited gadolinium enhancement with dural tail signs. Moreover, multiple foci of linear enhancement spreading through the sulci and into the nearby brain parenchyma were evident. At 1 month after parturition, en bloc removal of the mass, the attached dura mater and adjacent brain tissue was performed. Histologically, the mass located in the subdural space was composed of a mixture of B- and T-lymphocytes and plasma cells. Within the mass, multiple small lobules of meningothelial cells showing immunoreactivity for epithelial membrane antigen and vimentin were observed. The inflammatory cells had also infiltrated the subarachnoid and Virchow-Robin spaces, and the dura mater. The cerebral cortex showed ischemic changes, but no tumor cell invasion. On the basis of these histological features, the lesion appeared to be LPM with an inconspicuous meningothelial component and extensive inflammatory infiltration. This case appears to provide useful information on the pathogenesis of this variant.