A 3-year-old boy presents with pallor, petechiae, and hepatosplenomegaly. CBC shows WBC 95,000/mm³ with 85% blasts, Hb 6.2 g/dL, platelets 18,000/mm³. Bone marrow shows lymphoblasts with PAS-positive cytoplasm. Immunophenotyping: CD10+, CD19+, CD20−, TdT+. Which cytogenetic finding carries the BEST prognosis in this type of leukemia?
- A t(9;22) BCR-ABL1 (Philadelphia chromosome)
- B Hyperdiploidy >50 chromosomes with trisomy of chromosomes 4, 10, 17 ✓
- C t(4;11) MLL-AFF1 rearrangement
- D t(1;19) E2A-PBX1 translocation
Explanation
This is B-cell precursor acute lymphoblastic leukemia (BCP-ALL), confirmed by CD10+ (common ALL antigen), CD19+, TdT+, PAS-positive blasts. In BCP-ALL, hyperdiploidy with >50 chromosomes — particularly trisomies of chromosomes 4, 10, and 17 (called the 'triple trisomy') — is associated with an excellent prognosis (~90% long-term survival) due to enhanced sensitivity to methotrexate and thiopurines. t(9;22) (Philadelphia-positive ALL) is high-risk requiring TKI addition. t(4;11) involving MLL rearrangement (KMT2A-AFF1) is a high-risk feature associated with infant ALL and very poor prognosis. t(1;19) has intermediate risk.
Reference: Ghai Essential Pediatrics, 10th ed.
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