Single nucleotide polymorphism array-based karyotyping shows sequential genomic changes from monosomy to copy-neutral loss of heterozygosity of chromosome 7 and 20q deletion within a balanced translocation t(14;20) in AML.

Single nucleotide polymorphism array (SNP-A)-based karyotyping can identify copy-neutral loss of heterozygosity (CN-LOH) as well as cryptic lesions not detected by metaphase cytogenetics. We report serial genetic studies on a patient diagnosed with chronic myelomonocytic leukemia who progressed to acute leukemia. Monosomy 7 was predominantly found at diagnosis, but clones changed to CN-LOH of chromosome 7 with disease progression. Furthermore, subclones with genomic aberrations of 3q gain, 1p CN-LOH, and trisomy 12 newly appeared, suggesting that they were also involved in the transformation process. Additionally, by SNP-A, a presumably balanced translocation, t(14;20), identified by metaphase cytogenetics, was shown to result in an unbalanced 20q deletion at the breakpoint. The sequential changes identified by SNP-A may provide a better understanding of the mechanism of clonal evolution.