Which is the most common cytogenetic abnormality in adult acute myeloid leukemia (AML)?

Question

Accepted Answer

D. Complex karyotype (≥ 3 abnormalities). ## Cytogenetics of Adult AML

**Key Point:** Complex karyotype (defined as ≥ 3 unrelated cytogenetic abnormalities) is the single most common cytogenetic finding in adult AML, occurring in approximately 10–15% of cases. However, when considering balanced translocations, t(8;21) and inv(16) (collectively termed "core binding factor" AML) are the most frequent recurrent abnormalities.

### Frequency of Cytogenetic Abnormalities in Adult AML

| Abnormality | Frequency | Prognosis | WHO Classification |
|---|---|---|---|
| Complex karyotype | 10–15% | Adverse | AML with complex karyotype |
| t(8;21) RUNX1-RUNX1T1 | 5–10% | Favorable | AML with t(8;21) |
| inv(16) CBFB-MYH11 | 5–8% | Favorable | AML with inv(16) |
| t(15;17) PML-RARA | 5–8% | Favorable (with ATRA + arsenic) | APL |
| Monosomy 7 / del(7q) | 5–10% | Adverse | AML with monosomy 7 |
| TP53 mutations / del(17p) | 5–10% | Adverse | AML with TP53 mutation |
| Normal karyotype | 40–50% | Intermediate (depends on FLT3-ITD, NPM1) | AML with normal karyotype |

**High-Yield:** The 2022 WHO Classification emphasizes that cytogenetics and molecular mutations (FLT3-ITD, NPM1, CEBPA, TP53) are critical for risk stratification in AML. Complex karyotype is an independent adverse prognostic factor.

### Core Binding Factor (CBF) AML

- **t(8;21):** AML-M2 (AML with maturation); RUNX1-RUNX1T1
- **inv(16) or t(16;16):** AML-M4Eo (AML with eosinophilia); CBFB-MYH11
- **Favorable prognosis:** 5-year survival 50–60% with intensive chemotherapy
- **Sensitive to high-dose cytarabine**

**Clinical Pearl:** Patients with t(15;17) (APL) have an excellent prognosis (> 80% cure rate) with all-trans retinoic acid (ATRA) and arsenic trioxide (ATO), even though the karyotype itself is not "favorable" by traditional criteria. This is a paradigm shift in AML management.

**Mnemonic: "RUNX CBF"** — Remember t(8;21) and inv(16) as the favorable **C**ore **B**inding **F**actor abnormalities; RUNX1 is the gene in t(8;21).

Answer

A. t(8;21) — RUNX1-RUNX1T1

Answer

B. t(15;17) — PML-RARA

Answer

C. inv(16) — CBFB-MYH11

Which is the most common cytogenetic abnormality in adult acute myeloid leukemia (AML)?

Explanation

Cytogenetics of Adult AML

Frequency of Cytogenetic Abnormalities in Adult AML

Core Binding Factor (CBF) AML

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Abnormality	Frequency	Prognosis	WHO Classification
Complex karyotype	10–15%	Adverse	AML with complex karyotype
t(8;21) RUNX1-RUNX1T1	5–10%	Favorable	AML with t(8;21)
inv(16) CBFB-MYH11	5–8%	Favorable	AML with inv(16)
t(15;17) PML-RARA	5–8%	Favorable (with ATRA + arsenic)	APL
Monosomy 7 / del(7q)	5–10%	Adverse	AML with monosomy 7
TP53 mutations / del(17p)	5–10%	Adverse	AML with TP53 mutation
Normal karyotype	40–50%	Intermediate (depends on FLT3-ITD, NPM1)	AML with normal karyotype