A 4-year-old boy has a 3-week history of pallor, bone pain, fever, and hepatosplenomegaly. CBC: Hb 6.2 g/dL, WBC 85,000/mm3 with 80% lymphoblasts, platelets 28,000/mm3. Immunophenotyping shows CD19+, CD10+, TdT+, and cytoplasmic Ig negative. This immunophenotype is most consistent with:
- A T-cell ALL (T-ALL)
- B Pre-B ALL (common ALL) — favorable subtype ✓
- C Burkitt lymphoma/leukemia — mature B-ALL
- D AML with monocytic differentiation
Explanation
CD19+, CD10+ (CALLA — common ALL antigen), and TdT+ with negative cytoplasmic/surface Ig characterizes Pre-B ALL (common ALL, also called B-precursor ALL) — the most common pediatric leukemia (80% of ALL). TdT (terminal deoxynucleotidyl transferase) is expressed in pre-B and pre-T lymphoblasts, confirming lymphoblastic origin. CD10 positivity is a favorable prognostic marker. T-ALL expresses CD3, CD7, TdT, and lacks CD19/CD20. Mature B-ALL (Burkitt-type) expresses surface Ig and CD20, is TdT-negative, and is associated with t(8;14) c-myc rearrangement. AML expresses myeloid markers (CD13, CD33, CD117, MPO).
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.