This is a scary recent new finding about cancer in cats:
http://www.vetpathology.org/cgi/content/full/41/3/209
http://www.vetpathology.org/cgi/content/full/41/3/209
A recent study used a case control design to evaluate how environmental factors may be associated with the development of feline oral SCC. The results of this study demonstrated an association between the development of feline oral SCC and flea collar use, dietary tuna intake, and high canned food intake. Any household ETS was associated with a marginally significant twofold increase in risk, with the suggestion of an even greater increase in risk in cats exposed for 5 years or longer and those living with two or more smokers. Although this study showed some interesting associations, implication of any of these substances in the etiology of oral SCC would be stronger if a biologic link could be established.