A 3-year-old presents with a 3-week history of pallor, fever, lymphadenopathy, and hepatosplenomegaly. Bone marrow biopsy shows >25% lymphoblasts. Immunophenotyping: TdT positive, CD10 positive, CD19 positive, CD34 positive. Cytogenetics: t(12;21). Which statement CORRECTLY characterizes the prognosis of this cytogenetic finding?

• A t(12;21) is associated with Philadelphia chromosome and is the most common in adult ALL with poor prognosis
• B t(12;21) is associated with T-cell ALL and has an intermediate prognosis
• C t(12;21) causes MLL rearrangement and confers a poor prognosis, particularly in infants under 1 year
• D t(12;21) creating ETV6-RUNX1 fusion is the MOST COMMON cytogenetic abnormality in pediatric ALL and confers a FAVORABLE prognosis ✓

Explanation

The t(12;21)(p13;q22) translocation creates the ETV6-RUNX1 (formerly TEL-AML1) fusion and is the MOST COMMON chromosomal translocation in pediatric B-cell ALL (~25% of cases). It confers a favorable prognosis with 5-year event-free survival exceeding 90% with standard chemotherapy. It is not the Philadelphia chromosome (t(9;22), BCR-ABL1)—which is more common in adults and confers poor prognosis. t(12;21) is found in B-cell precursor ALL (TdT+, CD10+, CD19+), not T-ALL. MLL rearrangements (t(4;11) and others) affect infants and have poor prognosis.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.