2. Patient has relapsed or refractory CD20-positive disease following previous first-line systemic chemotherapy. Patients who have failed to achieve complete remission with previous chemotherapy are defined as refractory, and those who relapsed after an initial complete remission are classified as having relapsed. A biopsy must be performed to confirm diagnosis of relapsed disease. Tumor tissue within 6 months of Day 1 of Cycle 1 of study treatment will be used for the central review.