Figure 2.

For a single disease, in this case cancer, four persistent (stable) steady states exist toward which all other states move over time indicated by green arrows. In between these persistent (stable) steady states, threshold states exist. Depending on the disease and the immune parameter values four cases exist, the healthy case (A), the precancerous dormant case (B), the mild cancerous case (C), and the co-existing dormant fatal cancerous case (D). In the last case, the state ultimately approaches the dormant state or the fatal cancerous state. After having a single mutation, in this case, the immune system controls the clone and the state develops into the dormant state but after a severe perturbation crossing the threshold value, the state develops into fatal cancer.