Intrathecal Rituximab in Lymphoid Malignancies Involving Central Nervous System

The goal of this clinical research study is to learn about the safety and effectiveness of rituximab given by spinal tap in patients with lymphoid malignancies involving the central nervous system. A spinal tap (also called a lumbar puncture) is when fluid surrounding the spinal cord is collected by inserting a needle into the lower back. The affected area is numbed with local anesthetic during the procedure. It will also be used to give chemotherapy in this study. Rituximab is designed to bind to a protein, called CD20, that is on the surface of the leukemia cells. This may cause the leukemia cells to die.