A 62-year-old man has had fever and a 4-kg weight loss over the past 6 months. On physical examination, his temperature is 38.6deg C. He has generalized nontender lymphadenopathy, and the spleen tip is palpable. Laboratory studies show hemoglobin, 10.1 g/dL; hematocrit, 30.3%; platelet count, 140,000/mm3; and WBC count, 24,500/mm3 with 10% segmented neutrophils, 1% bands, 86% lymphocytes, and 3% monocytes. A cervical lymph node biopsy specimen microscopically shows a nodular pattern of small lymphoid cells. A bone marrow biopsy specimen shows infiltrates of similar small cells having surface immunoglobulins that are CD5+, but CD10-. Cytogenetic analysis indicates t (11;14) in these cells. What is the most likely diagnosis?