The outcomes of Moran dynamics. (a,d) Assuming that a mutant stem cell is present, stochastic dynamics will predict extinction of the mutant cell (a) or fixation (d). (b,c) However, fixation may require a long time - hence the clone may persist in a latent state (no disease) (b) or could reach a threshold leading to a disease state (c). At any of these steps, stochastic extinction is still possible, although less likely as the burden of mutant cells increases. Once the mutant clone reaches fixation (d) this is irreversible. Hence, the only two stable states are extinction or fixation.