Cancer is genetic metabolic disorder, untreatable and can be fatal. Whereas the cancerous cells are different from the normal cells. But what is driving force which switch a normal cell to cancerous cell?
Many complex factors are involved. Different cancers also have different predisposing factors and causes that eventually lead to the characteristic unregulated cell growth.
You may not be able to use it as an academic reference, but wikipedia has a very good article on cancer. http://en.wikipedia.org/wiki/Cancer
But If it is really the case, then what about the replication check points and the aurophagy. As in normal case, if there is any dysfunctioning or mutation in the cell, it will lead to apoptosis. So that's why it can be better to say as an unfortunate phenomena for the cell to turn out into a cancerous cell.