RATIONALE: Biological therapies, such as lenalidomide, may stimulate the immune system in different ways and stop cancer cells from growing. 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. It is not yet known whether lenalidomide is more effective with or without rituximab in treating chronic lymphocytic leukemia or small lymphocytic lymphoma.