A 4-year-old boy presents with pallor, bone pain, and lymphadenopathy. CBC shows WBC 80,000/μL with lymphoblasts. Immunophenotyping reveals TdT+, CD10+, CD19+, CD34+. Cytogenetics shows t(12;21) translocation. Which statement about this translocation is MOST accurate?
- A It generates a BCR-ABL1 fusion with constitutive tyrosine kinase activity
- B It generates an ETV6-RUNX1 fusion and carries the most favorable prognosis among ALL subtypes ✓
- C It is associated with KMT2A rearrangement and infant ALL with poor prognosis
- D It indicates Philadelphia chromosome–positive ALL requiring imatinib
Correct answer: B. It generates an ETV6-RUNX1 fusion and carries the most favorable prognosis among ALL subtypes
Explanation
The t(12;21)(p13;q22) translocation produces the ETV6-RUNX1 (previously TEL-AML1) fusion gene, found in approximately 25% of pediatric B-ALL cases. This is the most common chromosomal translocation in childhood leukemia and carries the most favorable prognosis among ALL cytogenetic subgroups, with event-free survival exceeding 90% with standard therapy. BCR-ABL1 arises from t(9;22), KMT2A rearrangements arise from 11q23 translocations in infant ALL, and Philadelphia chromosome–positive ALL carries a poor prognosis.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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