Figure 2.

Clone phylogeny (a) without branch lengths and (b) with branch lengths. In panel (a), three possible migration histories are shown, because the ancestral clone A2 may have been present in the primary tumor or in one of the two metastases. In panel (b), the most likely migration history is shown based on the clone phylogeny with branch lengths, because A2 is nearly identical to clone C2 (and genetically different from clones C1 and C3). Branch lengths provide crucial information. The information deducted by branch lengths can be used into giving insight for choosing the most likely migration path (P→M1→M2).