What is the most common chromosomal abnormality seen in Acute Myelogenous Leukemia (AML)?

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Most Common Chromosomal Abnormality in AML

The answer is B. t(8;21), which is one of the most frequent chromosomal abnormalities in AML, particularly in pediatric cases where it accounts for approximately 40% of FAB-M2 morphology AML. 1, 2

Why t(8;21) is the Correct Answer

Frequency in AML

  • t(8;21)(q22;q22) is among the most frequent chromosomal abnormalities in AML, particularly in children where it represents a substantial proportion of cases 1
  • In pediatric AML, t(8;21), inv(16), t(15;17), and 11q23/MLL-rearranged abnormalities together account for 50% of all cases, with t(8;21) being one of the most common within this group 1
  • The translocation accounts for 40% of pediatric AML with FAB-M2 morphology specifically 2

Clinical Significance

  • t(8;21) results in the RUNX1-RUNX1T1 fusion gene and is classified as favorable-risk AML 1
  • This translocation is one of only three genetic abnormalities (along with inv(16)/t(16;16) and t(15;17)) where the genetic abnormality alone is sufficient for AML diagnosis regardless of blast percentage 1, 3

Why the Other Options Are Incorrect

Option A: t(9;22) - Philadelphia Chromosome

  • t(9;22) is NOT a common abnormality in AML—it is the defining abnormality of chronic myeloid leukemia (CML) 1
  • In acute leukemia, t(9;22) is most commonly associated with acute lymphoblastic leukemia (ALL), where it represents 25% of adult ALL cases 1
  • When t(9;22) occurs in acute leukemia, it typically presents as mixed phenotype acute leukemia (MPAL) rather than pure AML 1

Option C: t(15;17)

  • t(15;17) is specific to acute promyelocytic leukemia (APL), which is a distinct subtype of AML but not the most common chromosomal abnormality overall 1
  • While t(15;17) is clinically important due to its unique treatment with ATRA, it represents only one specific AML subtype 1

Option D: TP53

  • TP53 is a gene mutation, not a chromosomal abnormality 1
  • While TP53 mutations occur in AML, particularly in therapy-related AML and complex karyotype cases, this is fundamentally a different category from chromosomal translocations 1

Additional Context on Common AML Cytogenetics

Core Binding Factor AML

  • t(8;21) and inv(16)/t(16;16) together comprise "core binding factor (CBF)-AML", which represents a favorable prognostic group 1
  • These abnormalities are much more frequent in pediatric AML (50% combined) compared to adult AML 1

Trisomy 8

  • Trisomy 8 is the most frequent numerical chromosome aberration in AML (7.6% overall incidence), but it is not a structural translocation like the options presented 4
  • Trisomy 8 typically occurs with other abnormalities and has intermediate prognosis when occurring alone 4

Common Pitfall to Avoid

  • Do not confuse the most common chromosomal abnormality in ALL (t(9;22) in adults) with AML—these are distinct diseases with different cytogenetic profiles 1
  • The Philadelphia chromosome t(9;22) is characteristic of CML and adult ALL, not AML 1

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

3
Guideline

Acute Myeloid Leukemia Classification and Diagnosis

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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