Does scratched Teflon coated frying pans contain carcinogens which can cause cancer?
Teflon is a polymer of perfluorooctanoic acid (PFOA) and related compounds.  PFOA is thought to be a carcinogen.  

I think there's an urban legend that if you really heat teflon up or burn it (it doesn't burn as flouroxides are not stable in air) that you might get some of the constituent chemicals out into the air.  

Once the flourocarbons are polymerized into fibers and surface coated a metal pan, they are chemically inert and aren't carcinogenic.  Teflon can be made to burn and some noxious fumes produced, but they are not especially carcinogenic.  

Even after all this, this paper reviewed PFOA exposure and points out that most people in industrialized countries have some PFOA in their blood and this does not seem to be related to a strong incidence of cancer as the level of exposure is so low. 

Flouro-carbon compounds are terribly inert - thats why teflon is so tough.  If PFOA is dangerous, then Teflon is > 10 million times less dangerous.  If PFOA is dangerous, crossing the street is many more times dangerous.  

Even PFOA will be eliminated from Teflon production, supposedly next year (2015).