Figure 1. Trunk and Branch model representing intratumour heterogeneity.

Common or ubiquitous events in the tumour found in every subclone and every tumour region are represented in the trunk of the tree. Diverse, heterogeneous somatic events are represented by the branches and the leaves. Tumour somatic events occurring in the trunk or branches may be driver or passenger events that may be dynamic during tumour evolution and adaptation to therapy (Adapted from Yap et al 2012). The figure illustrates key research areas and the need to identify how cancer therapeutics might influence intratumour heterogeneity.