Extranodal marginal zone B-cell lymphoma mimicking meningioma in lateral ventricle: a case report and possible pathogenesis.

We report a case of extranodal marginal zone B-cell lymphoma (MZL) mimicking meningioma in a lateral ventricle and suggest its possible pathogenesis. The patient was a 63-year-old male with seizure attack. MRI showed a 3.5x1.7 cm sized homogeneously enhancing mass in the trigon of the right lateral ventricle, possibly arising from the choroid plexus. The provisional diagnosis was meningioma or metastasis. In the surgical findings, the mass was attached to the choroid plexus and totally removed. Pathologic examination revealed a monotonous population of medium-sized mononuclear lymphoma cells associated with meningothelial whorl formation and neoplastic cells which invaded the meningothelial cells. The tumor was immunopositive for CD79a, CD20, CD43 and bcl-2. We suggest that intracranial extranodal marginal zone B-cell lymphomas might mimic meningiomas, because of their relation with the arachnoid cells and that meningothelial cells serve as a substitute for the mucosal surface in intracranial MALT lymphomas.