Well, it's extremely possible that it is cancer.. I mean, it's also possible that the smoking didn't do all of it, maybe it just triggered it? Some people just get cancer very easily
My grandfather(god bless his soul) had never smoked sun-bathed or anything his whole life and about 10 years ago he was diagnosed with prostate cancer and oral cancer. He's still living today! Cancer isn't unbeatable, although it is a very hard fight!
Hopefully this opens your eyes to the harmfulness of smoking.