A 16-year-old boy presents with a rapidly enlarging anterior mediastinal mass causing superior vena cava compression. Biopsy shows sheets of medium-sized blasts that are TdT positive by immunohistochemistry, express cytoplasmic CD3 and CD7, and lack surface immunoglobulin. What is the diagnosis?
- A Thymoma type B2
- B Primary mediastinal large B-cell lymphoma
- C T-lymphoblastic lymphoma ✓
- D Mediastinal germ cell tumor, seminoma type
Correct answer: C. T-lymphoblastic lymphoma
Explanation
T-lymphoblastic lymphoma typically affects adolescent males, arises in the thymus as a bulky anterior mediastinal mass, and shows TdT-positive T-cell precursor blasts expressing pan-T markers such as CD3 and CD7 without surface immunoglobulin. PMBL is a mature B-cell neoplasm that is TdT negative, seminoma expresses OCT3/4 and PLAP, and thymoma shows an admixture of epithelial tumor cells with non-neoplastic immature T cells.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.