Here is how I understand it:

DNA replication is not 100% perfect and error can happen, this error can be good(evolution) or bad(cancer properties). But its not the only source of cancer cells - DNA can be damaged by environment, and in rare cases it can receive cancer properties.

Am I correct?

  • $\begingroup$ Welcome to Biology.SE. I think this is a duplicate but I could not find the other post for the moment. $\endgroup$ – Remi.b Mar 25 '16 at 2:35
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    $\begingroup$ Yes, you are about correct. A cancer is an evolutionary process. There are selection pressures both at the multicellular levels and at the cell level. Note that the dichotomy are associated terms this error can be good(evolution) or bad(cancer properties) suggests some misunderstanding about what evolution is about. $\endgroup$ – Remi.b Mar 25 '16 at 2:38
  • $\begingroup$ @Remi.b this is not a duplicate of that. I do seem to remember another dupe... $\endgroup$ – AliceD Mar 25 '16 at 6:18