Meningeal vessels containing clusters of large neoplastic lymphocytes in a case of intravascular large B-cell lymphoma involving the central nervous system (CNS). The tumor cells were strongly positive for CD20 and CD79a. The adjacent brain parenchyma may show rarefaction due to ischemia resulting from vascular occlusion. The CNS manifestations are extremely variable and often bizarre depending upon the specific sites within the brain that are affected by ischemic changes. The patients may develop multiple cerebrovascular events, peripheral or cranial neuropathies, spinal cord lesions, or subacute encephalopathy.