A 65-year-old man is found to have WBC 145 × 10⁹/L with 92% mature lymphocytes. Flow cytometry shows CD5+, CD19+, CD23+, CD20(dim), sIg(dim), FMC7–. The MOST likely diagnosis is:
- A Chronic lymphocytic leukemia (CLL) ✓
- B Mantle cell lymphoma (MCL)
- C Follicular lymphoma
- D Prolymphocytic leukemia (PLL)
Correct answer: A. Chronic lymphocytic leukemia (CLL)
Explanation
CLL has the characteristic immunophenotype CD5+, CD19+, CD23+, CD20 (dim), surface Ig (dim), FMC7 negative, and CD22 (dim). This CD23 positivity and FMC7 negativity distinguishes CLL from mantle cell lymphoma, which is CD5+, CD23–, FMC7+, with Cyclin D1 overexpression due to t(11;14). Follicular lymphoma is CD5–. PLL has >55% prolymphocytes with a different clinical picture.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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