Disease progression over serial time points. (A) Sanger sequencing from 1 patient over 4 time points reveals a serial increase in the allelic fraction of mutant SETBP1 c.2608G>A (p.G870S). (B) Sequencing of individual colonies from the same patient using defrosted, cryopreserved cells grown in complete methylcellulose at diagnosis, relapse 1, and relapse 2 reveals that the number of cells that contain heterozygous and homozygous mutant SETBP1 increase despite intensive treatment. n = number of colonies sequenced at each time point.