A 7-year-old child presents with fever, pallor, and petechiae. Bone marrow examination shows 85% blasts. Flow cytometry reveals CD19+, CD10+, CD34+, TdT+. Which cytogenetic finding would best distinguish favorable-risk B-ALL from high-risk B-ALL in this patient?

Question

Accepted Answer

B. Hyperdiploidy (>50 chromosomes). ## Cytogenetic Risk Stratification in B-ALL

### Prognostic Cytogenetic Abnormalities

| Cytogenetic Finding | Prognosis | Frequency in Pediatric B-ALL |
|---------------------|-----------|------------------------------|
| **Hyperdiploidy (>50 chr)** | **Favorable** | ~25–30% |
| **t(12;21) TEL-AML1** | **Favorable** | ~20–25% |
| **t(9;22) Philadelphia** | **Adverse** | ~3–5% |
| **t(4;11) MLL rearrangement** | **Adverse** | ~5–10% |
| **Complex karyotype (≥3 abn)** | **Adverse** | ~5–10% |
| **Hypodiploidy (<45 chr)** | **Adverse** | ~5–10% |
| **Normal karyotype** | **Intermediate** | ~20–30% |

**Key Point:** Hyperdiploidy (>50 chromosomes) is one of the most favorable prognostic markers in pediatric B-ALL, associated with excellent long-term survival (>90%) with modern chemotherapy. This is a hallmark of common ALL (cALL) with CD19+, CD10+ immunophenotype.

**High-Yield:** The patient's immunophenotype (CD19+, CD10+, CD34+, TdT+) is consistent with **common ALL (cALL)**, which frequently harbors favorable cytogenetics. Hyperdiploidy and t(12;21) TEL-AML1 are the two most common favorable findings in cALL and are strong predictors of chemotherapy responsiveness.

**Clinical Pearl:** Philadelphia chromosome [t(9;22)] is the single most adverse prognostic factor in B-ALL, occurring in ~3% of pediatric cases and ~20% of adult cases. Its presence mandates intensive chemotherapy ± tyrosine kinase inhibitor (TKI) therapy. Complex karyotype also portends poor prognosis and requires intensified treatment.

**Mnemonic:** **FISH for FATE: Favorable = Hyperdiploidy, t(12;21); Adverse = t(9;22), t(4;11), Complex karyotype**

Answer

A. Complex karyotype with ≥3 abnormalities

Answer

C. t(9;22) Philadelphia chromosome

Answer

D. t(12;21) TEL-AML1 fusion

Cytogenetic Finding	Prognosis	Frequency in Pediatric B-ALL
Hyperdiploidy (>50 chr)	Favorable	~25–30%
t(12;21) TEL-AML1	Favorable	~20–25%
t(9;22) Philadelphia	Adverse	~3–5%
t(4;11) MLL rearrangement	Adverse	~5–10%
Complex karyotype (≥3 abn)	Adverse	~5–10%
Hypodiploidy (<45 chr)	Adverse	~5–10%
Normal karyotype	Intermediate	~20–30%

A 7-year-old child presents with fever, pallor, and petechiae. Bone marrow examination shows 85% blasts. Flow cytometry reveals CD19+, CD10+, CD34+, TdT+. Which cytogenetic finding would best distinguish favorable-risk B-ALL from high-risk B-ALL in this patient?

Explanation

Cytogenetic Risk Stratification in B-ALL

Prognostic Cytogenetic Abnormalities

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