Characterization of Three-Way Translocation [t(4;9;22)(p16;q34;q11.2)] in Chronic Myeloid Leukemia

The Philadelphia (Ph) chromosome, consisting of the t(9;22)(q34;q11.2) is observed in 90% with chronic myeloid leukemia (CML), while variant translocations are observed in 5 to 10%. In variant translocations, three way translocations are rare. We report two cases of three way translocation involving chromosomes 4, 9 and 22. Bone-marrow was subjected to conventional cytogenetic and fluorescence in situ hybridization (FISH) and three way translocation was identified as 46,XX,t(4;9;22)(p16;q34;q11.2). Although other chromosomes are frequently involved in three-way translocation, chromosome 4 is very rare event. So far five cases have been reported in the literature with translocation involving 4p16. We present a six case of chronic myeloid leukemia having 4p16 breakpoints whose clinical interpretation is still unclear.