Evolution of the malignant clone in PBMC samples. As the tumors were considered to be clonal, the assumption was made that all high-frequency variants detected in the tumor tissue samples occurred within a single clone, which progressively accumulates additional mutations over time. Variants were manually clustered into groups according to the VAF of each variant at each time point (see supplemental Figure 2A-F). The mean VAF of variants in each cluster at each time point was normalized to the maximum VAF of tumor-associated variants detected in the blood (vertical height of fishplot at time zero = maximum VAF of all tumor-associated variants in the blood, using the formula: (mean VAF of a cluster of variants at a given time point)/(maximum VAF of all tumor-associated variants observed in the blood at any time point). The first time point at which a cluster containing driver mutations was detected is labeled in each case. Subdominant and tumor-only variants were excluded from this analysis and are listed on the right-hand side. Vertical lines indicate the time points at which targeted deep sequencing was carried out using the PSTS probe panel. Time zero indicates the time point at which each individual was diagnosed with ATL.