Emergence of two unrelated clones in acute myeloid leukemia with MLL-SEPT9 fusion transcript

We report a case of acute myeloid leukemia (AML) with two unrelated clones, one of which was t(11;17)(q23;q25) carrying MLL-SEPT9 fusion transcripts. The patient was a 71-year-old man who was diagnosed with AML M0 and received multiple chemotherapy regimens, including DNA topoisomerase II inhibitors. Although the karyotype of bone marrow cells at the initial diagnosis was normal, two unrelated chromosomal aberrations concurrently appeared during the course of the disease, suggestive of t(11;17)(q23;q25) and add(1)(p36.1),del(6)(q?) by G-banding. Spectral karyotyping analysis identified a reciprocal translocation between chromosomes 11 and 17, and a translocation of the q arm of chromosome 6 to chromosome 1. Dual-color fluorescence in situ hybridization analysis that used probes specific for MLL in combination with tel 1p and tel 1q revealed a translocation of 1p→pter to chromosome 6 and a translocation of 11q23→qter to chromosome 17. Reverse transcriptase–polymerase chain reaction and sequencing analyses demonstrated MLL-SEPT9 fusion transcripts with the breakpoint of MLL exon 8/SEPT9 exon 2 and MLL exon 9/SEPT9 exon 2. Thus, the karyotype was defined as 46,XY,t(11;17)(q23;q25)/46,XY,t(1;6)(p36.3;q23). Our case represents an additional MLL-SEPT9-positive AML that was considered to be related to therapy.