A 4-year-old boy presents with pallor, petechiae, and a 2-week history of bone pain. CBC shows WBC 65,000/μL with 80% blasts, hemoglobin 6.8 g/dL, and platelets 18,000/μL. Bone marrow confirms B-cell ALL. Cytogenetics shows ETV6-RUNX1 (t(12;21)) translocation. Which statement about this cytogenetic finding is MOST accurate regarding prognosis?
- A ETV6-RUNX1 is associated with high risk and requires intensified therapy
- B ETV6-RUNX1 is the most common chromosomal translocation in pediatric ALL and confers a favorable prognosis ✓
- C ETV6-RUNX1 indicates Philadelphia chromosome-like ALL with poor prognosis
- D This translocation is detectable by conventional karyotype in most cases
Explanation
The ETV6-RUNX1 fusion (t(12;21)/p13;q22), also called TEL-AML1, is the most common chromosomal translocation in pediatric B-cell ALL occurring in approximately 25% of cases. It is a strongly favorable prognostic marker associated with event-free survival >90% with standard treatment protocols. Critically, this translocation is cryptic on conventional karyotype (the chromosomes appear normal) and requires FISH or RT-PCR for detection — this is an important clinical point. Philadelphia chromosome-like (BCR-ABL1-like) ALL is a high-risk subset with poor prognosis. Hyperdiploid ALL (>50 chromosomes) is another favorable cytogenetic finding.
Reference: Ghai Essential Pediatrics, 10th ed.
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