t(8;21)(q23;q22), a Novel Translocation Involving the RUNX1 Gene in a Patient with Acute Myeloid Leukemia

Area of Science:

• Hematology
• Cytogenetics
• Molecular Biology

Background:

• Chromosome translocations involving the RUNX1 gene are common in acute myeloid leukemia (AML).
• The t(8;21)(q22;q22) translocation, resulting in the RUNX1::RUNX1T1 fusion gene, defines a distinct AML subtype.
• Accurate identification of translocations is crucial for diagnosis and classification.

Purpose of the Study:

• To investigate a case of AML with an initial diagnosis suggestive of t(8;21)(q22;q22) translocation.
• To clarify the genetic abnormality when standard tests for RUNX1::RUNX1T1 fusion are negative.
• To re-evaluate cytogenetic findings using integrated molecular and cytogenetic data.

Main Methods:

• Initial cytogenetic analysis (karyotyping) to detect chromosome translocations.
• Fluorescence in situ hybridization (FISH) to specifically identify the RUNX1::RUNX1T1 fusion gene.
• Reverse transcriptase polymerase chain reaction (RT-PCR) to detect RUNX1::RUNX1T1 fusion transcripts.
• Reassessment of karyotyping in conjunction with FISH and RT-PCR results.

Main Results:

• Initial karyotyping suggested a t(8;21)(q22;q22)-like translocation.
• FISH analysis failed to detect the RUNX1::RUNX1T1 fusion signals.
• RT-PCR also did not confirm the presence of the RUNX1::RUNX1T1 fusion gene.
• Re-evaluation of cytogenetics identified a variant translocation, t(8;21)(q23;q22).

Conclusions:

• The study highlights the importance of integrating multiple diagnostic techniques in AML.
• Atypical presentations of common translocations require careful reassessment.
• The identified t(8;21)(q23;q22) translocation represents a distinct genetic event in this AML case, differing from the canonical t(8;21)(q22;q22).