In WHO 2022 classification, primary mediastinal large B-cell lymphoma (PMBL) is characterized by which immunophenotypic and molecular signature that distinguishes it from classic DLBCL?
- A CD10+, BCL6+, MUM1– (germinal center B-cell phenotype); MYC translocation
- B CD30+, CD23+, MAL gene overexpression; PD-L1 and PD-L2 amplification at 9p24 ✓
- C CD5+, cyclin D1+; t(11;14) translocation
- D BCL2 overexpression due to t(14;18); follicular cell morphology
Correct answer: B. CD30+, CD23+, MAL gene overexpression; PD-L1 and PD-L2 amplification at 9p24
Explanation
PMBL has a distinct molecular signature overlapping with nodular sclerosis classical Hodgkin lymphoma: CD30 expression, CD23 positivity (unusual for DLBCL), MAL and PDCD1LG2/CD274 (PD-L1/PD-L2) overexpression due to amplification at 9p24.1, and lack of surface immunoglobulin. The 9p24 amplification also upregulates JAK2. This PD-L1/L2 upregulation is the rationale for pembrolizumab in relapsed PMBL. Cyclin D1/t(11;14) is mantle cell lymphoma; t(14;18)/BCL2 is follicular lymphoma.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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