A 52-year-old woman is evaluated for a 3-month history of enlarged bilateral axillary lymph nodes. She has also recently developed fever, weight loss, and night sweats. Medical history is unremarkable, and she takes no medications.
On physical examination, temperature is 38.5 °C (101.3 °F), blood pressure is 100/60 mm Hg, pulse rate is 90/min, and respiration rate is 14/min. Firm bilateral axillary lymph nodes are palpated. Splenomegaly is present. The remainder of the examination is unremarkable.
Hemoglobin | 9.0 g/dL (90 g/L) |
Leukocyte count | 18,000/μL (18 × 109/L) |
Platelet count | 70,000/μL (70 × 109/L) |
Lactate dehydrogenase | Elevated |
β2-microglobulin | Elevated |
CT scans of the chest, abdomen, and pelvis show bilateral enlarged axillary and intra-abdominal lymph nodes and an enlarged spleen. Axillary lymph node excisional biopsy reveals diffuse infiltration with small monoclonal lymphoid cells with CD20+ and cyclin D1 overexpression. Subsequent colonoscopy is performed, and biopsy indicates mucosal infiltration with lymphoid cells expressing B-cell markers.
Which of the following is the most likely diagnosis?