I remember when "oncogenes" were on the cover of TIME. They were the key to understanding malignancy, and would change the ballgame. That was about 30 years ago.
Now that handful of oncogenes have become tens of thousands of mutations ...
BBC News - Scientists crack 'entire genetic code' of cancerWe used to think a cancer involved a few mutations. Maybe two or three. Not 23,000.... scientists found the DNA code for a skin cancer called melanoma contained more than 30,000 errors almost entirely caused by too much sun exposure.
The lung cancer DNA code had more than 23,000 errors largely triggered by cigarette smoke exposure.From this, the experts estimate a typical smoker acquires one new mutation for every 15 cigarettes they smoke.Although many of these mutations will be harmless, some will trigger cancer...
It takes an astounding number of mutations to knock off the systems that prevent cancer -- while managing not to kill the cell.
Among other things we now have a good explanation of why cancer risk falls after someone stops smoking. It appears that the mutated cells are replaced by healthy cells. If they're lucky the bad ones die off before one goes rogue.
So it's never too late to stop - or to get out of the sun.