A 5-year-old boy presents with pallor, bone pain, hepatosplenomegaly, and lymphadenopathy. CBC shows WBC 80,000/mm3 with 85% blasts. Blast morphology shows lymphoblasts with TdT positive, CD10+, CD19+ markers. What is the MOST common cytogenetic abnormality associated with the BEST prognosis in this condition?

• A t(9;22) Philadelphia chromosome
• B t(4;11) MLL rearrangement
• C High hyperdiploidy (>50 chromosomes)
• D t(12;21) ETV6-RUNX1 (TEL-AML1) ✓

Explanation

This is B-cell Acute Lymphoblastic Leukemia (B-ALL), the most common childhood cancer. t(12;21) creating ETV6-RUNX1 (TEL-AML1) fusion is the MOST COMMON cytogenetic abnormality in B-ALL (~25%) and carries the BEST prognosis with 5-year OS >90% with standard chemotherapy. Philadelphia chromosome t(9;22) carries the worst prognosis. High hyperdiploidy also has good prognosis but is less common than ETV6-RUNX1. The overall cure rate for childhood ALL exceeds 85% with modern protocols.

Reference: Ghai Essential Pediatrics, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.