But you haven't posted anything that shows nicotine IS a suspected carcinogen, either? In order for a substance to be considered a "suspected carcinogen" there would usually be a general consensus in the scientific community. MOST things we call "carcinogens" are "suspected" but not proven. The
American Cancer Society states, "based on how hard it can be to test these candidate carcinogens, most are listed as being of probable, possible, or unknown risk. Only a little over 100 are classified as carcinogenic to humans." Note that nicotine is not on any of the known, probable or possible carcinogens lists.
One or two studies, studies that only conclude that more studies need to be done to find if there is more supporting evidence of what they found, does not automatically make something a "suspected carcinogen."
ETA - sorry, I just picked up on that comment after I re-read your post. Not trying to beat a dead horse, but I thought it should be pointed out. Part of the reason we are in such a pickle is people have such a vast misunderstanding of what makes something "hazardous." That's why they buy the "anti freeze" and "carcinogen" claims the ANTZ make about e-cigarettes. I blame, in large part, the media that is so quick to jump on every small study and proclaim it as undeniable proof of something.
OK. You'll note that I asked what you meant by 'suspected carcinogen' earlier in the thread. I wasn't sure whether that is a 'term of art', or just meant something that real scientists reasonably suspect is a carcinogen (as vague as that may be).
If the latter, then I've posted links to search terms which point to papers mostly discussing evidence of in vitro cancerous mutations caused by metabolites of nicotine (I don't know if that would be enough to count something a 'carcinogen'), but some seemingly by nicotine itself.
EDIT (added after some of the replies below were posted) -
You'll note that various MSDS's describe it as mutagenic (normally in yeast, sometimes apparently in lab animals, though I haven't seen that MSDS myself), and the CDC thinks that nicotine's status with respect to carcinogenicity is 'inconclusive'.
http://www.cdc.gov/niosh/ershdb/EmergencyResponseCard_29750028.html
EFFECTS OF CHRONIC OR REPEATED EXPOSURE: Nicotine is a teratogen (capable of causing birth defects). Other developmental toxicity or reproductive toxicity risks are unknown. The information about nicotine as a carcinogen is inconclusive.
Here are a few random examples - though as I've repeatedly stated, I'm not a scientist and can't attest to their quality.
http://toxsci.oxfordjournals.org/content/79/1/1.full - this one's interesting, though quite old now.
http://www.sciencedirect.com/science/article/pii/S0024320512001890 - animal model, abstract
http://www.treatobacco.net/en/page_62.php - states that nicotine metabolises to known carcinogens, and may be carcinogenic in hyperoxic hamsters.
http://cancerres.aacrjournals.org/content/69/21/8236.short - more evidence of carcinogenic metabolites.
http://carcin.oxfordjournals.org/content/33/9/1745.short - evidence of nicotine playing havoc with the pancreas.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3371638/ - "Over the past two decades, experimental models using animals, cell cultures, and clinical data have identified nicotine as a carcinogen for virtually all GI organs"
http://cancerprevres.aacrjournals.org/content/4/11/1719.short - "Laboratory studies have indicated a carcinogenic potential of nicotine"
http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0714.2008.00659.x/abstract - in vitro, abstract.
There are doubtless many others, these came from the first few pages of searches.
I could accept "Not widely regarded as a carcinogen", "Thought not to be carcinogenic in itself, though it may metabolise to known carcinogens", or "Displays no evidence of carcinogenicity at relevant doses", perhaps. But "Not a suspected carcinogen" still doesn't sound right, unless 'suspected carcinogen' has some special definition I'm not aware of.
Another thing I'll state is that if it is a carcinogen, it doesn't bother me in itself. Pesto and toast may be carcinogenic, I still eat them (not together - what kind of philistine do you take me for

). I still fly on planes, or get X-rayed when necessary. The fact that the public are poorly educated when it comes to understanding risk, and science generally, does not give us license to avoid 'scary' words, if they are the correct ones.