Figure 3. Cancer recapitulates evolution.

Within a developing tumor mutations accumulate over time as a result of unrepaired DNA damage. Most of these are either neutral or detrimental; only a small number bestow a cell with growth and survival benefits. These beneficial variants will preferentially multiply and produce additional mutations that may undergo further selection and expansion. Adventagous phenotypes for tumor growth include, among others, the ability to divide independently of extracellular signals (yellow), the ability to recruit a blood supply (green) and the ability to invade adjacent and distant tissues (blue). After overcoming all antineoplastic defense mechanisms, a tumor may proliferate indefinitely until the death of the host.