A 2-year-old child presents with pallor, recurrent infections, and petechiae. CBC: Hb 6 g/dL, WBC 120,000/μL with 85% blasts, platelets 18,000/μL. Flow cytometry shows CD10+, CD19+, TdT+, CD34+ blasts. The specific cytogenetic finding associated with the BEST prognosis in this type of ALL is:

• A t(9;22) — BCR-ABL1 (Philadelphia chromosome)
• B t(4;11) — KMT2A rearrangement
• C t(1;19) — TCF3-PBX1
• D High hyperdiploidy (>50 chromosomes) ✓

Explanation

The flow cytometry pattern (CD10+, CD19+, TdT+, CD34+) identifies B-cell precursor ALL (pre-B ALL), the most common childhood leukemia. High hyperdiploidy (≥51–65 chromosomes) is found in 25–30% of pediatric B-ALL and is associated with the best prognosis (event-free survival >90%) because hyperdiploid cells show increased sensitivity to antimetabolites, particularly methotrexate and thioguanine. t(9;22) (Philadelphia chromosome) confers poor prognosis. t(4;11)/KMT2A is associated with infant ALL and very poor prognosis. t(1;19) has intermediate prognosis.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.