A 68-year-old man has leukocytosis (WBC 85,000/µL) with 92% lymphocytes on differential. Lymphocytes are small, mature-appearing, with smear cells. Flow cytometry shows CD5+, CD19+, CD23+, CD20 (dim), surface Ig (dim), FMC7−. What is the diagnosis?
- A Chronic lymphocytic leukemia ✓
- B Mantle cell lymphoma
- C Prolymphocytic leukemia
- D Follicular lymphoma with leukemic phase
Correct answer: A. Chronic lymphocytic leukemia
Explanation
CLL has a characteristic immunophenotype: CD5+, CD19+, CD23+, dim CD20, dim surface immunoglobulin, and FMC7−. The CD5 and CD23 co-expression distinguishes CLL from mantle cell lymphoma (CD5+, CD23−, cyclin D1+). Smudge cells (smear cells) are characteristic of CLL. Prolymphocytic leukemia has >55% prolymphocytes (larger cells with prominent nucleolus) and CD23−.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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