RATIONALE: Lenalidomide may stop the growth of cancer cells by blocking blood flow to the cancer. Monoclonal antibodies, such as rituximab, can block cancer growth in different ways. Some block the ability of cancer cells to grow and spread. Others find cancer cells and help kill them or carry cancer-killing substances to them. Drugs used in chemotherapy, such as cyclophosphamide and dexamethasone, work in different ways to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. Giving lenalidomide together with rituximab, cyclophosphamide, and dexamethasone may kill more cancer cells.