Figure 1.

Linear and Branched Cancer Evolution. Schematic illustrating different patterns of cancer evolution. Intercellular heterogeneity followed by clonal selection leads to outgrowth of one or more subclones. If the emerging subclone outcompetes the rest of the tumour cell population, this is described as a clonal sweep, and the subclonal genotype has ‘fixed’ in the population. In linear evolution, subclones arise sequentially (top panel), while if divergent subclones emerge independently then evolution is branched (bottom panel). Incomplete clonal sweeps will generate clonal heterogeneity, which can arise in both linear and branch evolutionary trajectories. Subclonal genotypes allow the monitoring of tumour evolution over time.