A 62-year-old man has generalized lymphadenopathy and lymphocytosis of 25,000/µL. Flow cytometry shows B cells expressing CD19, surface IgM (bright), CD5, FMC7, and strong cyclin D1, but CD23 is negative. Which diagnosis best explains this immunoprofile?

• A Chronic lymphocytic leukemia
• B Marginal zone lymphoma
• C Follicular lymphoma leukemic phase
• D Mantle cell lymphoma ✓

Explanation

Mantle cell lymphoma shares CD5 positivity with CLL but differs by being CD23 negative, FMC7 positive, with brighter surface IgM and cyclin B1 overexpression driven by the t(11;14) CCND1-IGH rearrangement. CLL characteristically shows dim surface Ig, CD23 positivity, FMC7 negativity, and weak or absent cyclin B1. Follicular lymphoma expresses CD10 rather than CD5, and marginal zone lymphoma is typically CD5 and CD10 negative with no cyclin B1 expression.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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