A New Complex Translocation (15;20;17)(q22;p13;q21) in Acute Promyelocytic Leukemia

We describe here a 39-year-old male with acute promyelocytic leukemia (APL) carrying a new complex translocation (15;20;17). A chromosomal analysis of the bone marrow cells showed 46,XY, t(15;20;17)(q22;p13;q21). Fluorescence in situ hybridization (FISH) analysis using plasmid DNA libraries of chromosomes 15, 17, and 20 revealed three derivative chromosomes, der(15)t(15;17), der(17)t(17;20), and der(20)t(15;20). Fluorescence in situ hybridization with cosmid DNA probes flanking the breakpoints of t(15;17) did not show the retinoic acid receptor α (RARα)/PML fusion signal usually generated on the der(17)t(15;17). However, rearrangement of the RARα gene and expression of the PML/RARα chimeric transcript were identified by Southern blot and reverse-transcriptase polymerase chain reaction (RT–PCR) analyses, respectively. Our results confirmed that the PML/RARα gene on the der(15)t(15;17), not the RARα/PML gene, must be essential to leukemogenesis in APL. Furthermore, considering another reported case with a 20p13 aberration, it is possible that 20p13 is a nonrandom breakpoint in APL with a complex translocation.