Not all cancer cells are equal. They vary, they compete, and the fittest survive to pass on their genes to daughter cells, which continue to vary, compete and survive. If this sounds familiar, it’s because it is; cancer cells evolve
If a cancer cell acquires a mutation that enables it to grow faster, or survive longer and produce more offspring than the surrounding cells without that mutation, then that cancer cell has a selective advantage. Its descendants will be fitter; they will outgrow and dominate the local tissue environment.
Read the full, original story here: Hallmarks of Cancer 7: Genome Instability and Mutation