A 35-year-old man presents with fever, lymphadenopathy, and a mediastinal mass. Biopsy shows cells with immunophenotype CD2+, CD3+, CD4+, CD8−, CD1a+, TdT+. The diagnosis is:
- A Diffuse large B-cell lymphoma
- B Nodular sclerosis Hodgkin lymphoma
- C T-lymphoblastic lymphoma/leukemia ✓
- D Anaplastic large cell lymphoma
Correct answer: C. T-lymphoblastic lymphoma/leukemia
Explanation
CD1a, TdT (terminal deoxynucleotidyl transferase), and a T-cell immunophenotype (CD2, CD3) identify this as T-lymphoblastic lymphoma/leukemia, which typically presents with mediastinal mass in adolescent males. The CD4+/CD8− phenotype reflects a cortical thymocyte stage of maturation. Hodgkin lymphoma (nodular sclerosis) shows CD15+, CD30+ Reed-Sternberg cells and lacks TdT. ALCL is CD30+ with ALK rearrangement and TdT-negative. DLBCL expresses CD20.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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