Um. No, it is not well established. Nicotine, alone, has NOT been shown to be mutagenic. If you actually read the first article you cited, it states “Although a great deal of work has been carried out on the mutagenicity of the common PAHs found in cigarettes, only a few studies have addressed the genotoxic nature of nicotine itself.” Mainly, nicotine binds to nicotinic acetylcholine receptors to mediate its physiologic effects. There are scattered reports suggesting that nicotine might be carcinogenic, but the studies are faulty, and there are no clear cut molecular mechanisms to tie nicotine to cancer. So, in summary, nicotine has not been proven to be a carcinogen. You can see here in a university carcinogen database that there is no evidence in rats for its carcinogenic potential.
I would add that there are ~300K hits mainly because in many articles, you’ll find nicotine and carcinogen co-cited, not because they are linked.