A 4-year-old boy presents with a 2-week history of pallor, fatigue, and easy bruising. CBC shows WBC 85,000/µL with predominantly blast cells (90% blasts on smear), Hb 6.5 g/dL, and platelets 18,000/µL. Bone marrow biopsy confirms ALL. Immunophenotyping shows CD10+, CD19+, TdT+, CD34+. Which cytogenetic finding, if present, would indicate the BEST prognosis?
- A Philadelphia chromosome t(9;22)
- B t(4;11) MLL-AF4 rearrangement
- C t(1;19) TCF3-PBX1 rearrangement
- D Hyperdiploidy (>50 chromosomes) ✓
Explanation
In B-cell ALL (CD10+, CD19+, TdT+ pre-B ALL), hyperdiploidy (>50 chromosomes, especially gain of chromosomes 4, 10, 17) confers the BEST prognosis with >90% long-term survival with standard chemotherapy. Philadelphia chromosome t(9;22) (BCR-ABL1) indicates very poor prognosis (though tyrosine kinase inhibitors have improved this). t(4;11) with MLL-AF4 rearrangement is associated with infant ALL and very poor prognosis. t(1;19) TCF3-PBX1 was historically poor but responds well to intensified therapy. Hyperdiploidy increases sensitivity to antimetabolites (methotrexate, mercaptopurine).
Reference: Ghai Essential Pediatrics, 10th ed.
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