RUNX1 mutation associated with clonal evolution in relapsed pediatric acute myeloid leukemia with t(16;21)(p11;q22).

TLS/FUS-ERG chimeric fusion transcript resulting from translocation changes involving chromosomes 16 and 21 is a rare genetic event associated with acute myeloid leukemia (AML). The distinct t(16;21) AML subtype exhibits unique clinical and morphological features and is associated with poor prognosis and a high relapse rate; however, the underlying mechanism remains to be clarified. Recently, whole-genome sequencing revealed a large set of genetic alterations that may be relevant for the dynamic clonal evolution and relapse pathogenesis of AML. Here, we report three pediatric AML patients with t(16;21) (p11; q22). The TLS/FUS-ERG fusion transcript was detected in all diagnostic and relapsed samples, with the exception of one relapsed sample. We searched for several genetic lesions, such as RUNX1, FLT3, c-KIT, NRAS, KRAS, TP53, CBL, ASXL1, IDH1/2, and DNMT3A, in primary and relapsed AML samples. Interestingly, we found RUNX1 mutation in relapsed sample of one patient in whom cytogenetic analysis showed the emergence of a new additional clone. Otherwise, there were no genetic alterations in FLT3, c-KIT, NRAS, KRAS, TP53, CBL, ASXL1, IDH1/2, or DNMT3A. Our results suggest that precedent genetic alterations may be essential to drive the progression and relapse of t(16;21)-AML patients.