First case of iAMP21 was described with more than 12 signals for RUNX1 per cell and confirmation in SNP array, the second had confirmed 8–9 copies of RUNX1 in leukemia clone with karyotype 47,inc/46,XX, and the third 6–9 copies of RUNX1 per cell and karyotype 46,XY,− 21,+ mar. Here, RUNX1 is linked to leukemia.