A 70-year-old man presents with absolute lymphocytosis of 60,000/µL of small mature-appearing lymphocytes. He is asymptomatic. Flow cytometry shows CD19+, CD5+, CD23+, CD10- with weak surface IgM. This phenotype is diagnostic of:
- A Mantle cell lymphoma
- B Chronic lymphocytic leukemia (CLL) ✓
- C Marginal zone lymphoma
- D Follicular lymphoma
Correct answer: B. Chronic lymphocytic leukemia (CLL)
Explanation
CLL is characterized by the immunophenotype CD19+, CD5+, CD23+, weak surface immunoglobulin—the CD5/CD23 co-expression distinguishes CLL from mantle cell lymphoma (MCL). MCL is CD5+ but CD23-negative and overexpresses Cyclin D1 due to t(11;14). Marginal zone lymphoma is CD5-/CD23-; follicular lymphoma is CD10+/BCL2+ but CD5-negative.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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