Acute Promyelocytic Leukemia with i(17)(q10)

Area of Science:

• Hematology
• Cytogenetics
• Molecular Biology

Background:

• Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia.
• The hallmark genetic abnormality in APL is the t(15;17) translocation, leading to the PML/RARα fusion gene.
• Chromosomal abnormalities play a crucial role in the pathogenesis and classification of hematologic malignancies.

Observation:

• A rare case of APL with complex chromosomal abnormalities is presented.
• The patient exhibited multiple APL derivative clones, including a clone with an isochromosome 17q, denoted as i(17)(q10).
• This i(17)(q10) clone harbored a cryptic t(15;17) translocation, not microscopically obvious on the isochromosome itself.

Findings:

• Interphase fluorescence in situ hybridization (FISH) confirmed the presence of PML/RARα fusion signals within the i(17)(q10) clone.
• Detailed cytogenetic analysis revealed that the i(17)(q10) clone evolved from a classic t(15;17) clone through an intermediate cryptic t(15;17) clone.
• This indicates a complex evolutionary pathway of chromosomal aberrations in APL.

Implications:

• This finding expands the spectrum of known chromosomal abnormalities in APL.
• Understanding these complex rearrangements is vital for accurate diagnosis and risk stratification in APL patients.
• The study highlights the utility of integrated cytogenetic and molecular analyses for characterizing rare genetic events in leukemia.