A Novel Translocation (4;12)(q11;q13) in an Acute Promyelocytic Leukemia-Like Case Lacking RARα Rearrangements.

We report a novel chromosomal translocation t(4;12)(q11;q13) in a 37-year-old male with acute promyelocytic leukemia (APL)-like morphologic changes but lacking RARα rearrangements. His blast cells had some morphologic features evocative APL such as heavy azurophilic granules, bundles of Auer rods except regular round or oval nuclei. Immunophenotype of blast cells showed positivity for CD13 and CD33, and negativity for CD34 and HLA-DR which were compatible with the diagnosis of APL. Disseminated intravascular coagulation (DIC) was present. Chromosome study of BM cells showed that 29 out of 35 metaphases had a consistent karyotype of 46, XY, t (4;12)(q11;q13) which was confirmed by chromosome painting with whole chromosome paint probes 4 and 12. However, fluorescence in site hybridization, reverse transcriptase-polymerase chain reaction (RT-PCR) and multiplex RT-PCR did not demonstrate any evidence for RARα rearrangements including PML-RARα, PLZF-RARα, NuMA-RARα, NPM-RARαand STAT5b-RARα fusion genes. Sequential treatment with arsenic trioxide and chemotherapy had no effect, he died of bleeding due to DIC. In view of the fact as mentioned above, this case should be rated as transitional M2–M3.