Fig. 1.

Overview of several types of cancer progression models. For models with deterministic dependencies (a-e) $A\to B$ denotes that A is necessary for B, and $A⊣B$ denotes that A prevents B. For models with stochastic dependencies (f,g) $A\to B$ denotes that A makes B more likely, and $A⊣B$ denotes that A makes B less likely. In (d-e) the arrows between groups of events denote that at least one of the events in the parent group is necessary for the events in the child group