The process of malignancy can be explained from an evolutionary perspective. Millions of years of biological evolution insure that the cellular metabolic changes that enable cancer to grow occur only very rarely. Most changes in cellular metabolism that allow cells to grow in a disorderly fashion lead to cell death. Cancer cells undergo a process analogous to natural selection, in that the few cells with new genetic changes that enhance their survival continue to multiply, and soon come to dominate the growing tumor, as cells with less favorable genetic change are outcompeted. This process is called clonal evolution. Tumors often continue to evolve in response to chemotherapy treatments, and on occasion aberrant cells may acquire resistance to particular anti-cancer pharmaceuticals.
Cancer - How Its Happen
When normal cells are damaged beyond repair, they are eliminated by apoptosis (A). Cancer cells avoid apoptosis and continue to multiply in an unregulated manner (B).
Cancer
Cancers are caused by a series of mutations. Each mutation alters the behavior of the cell somewhat.
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