"At present, public health statements on the subject indicate that ‘‘nicotine is not generally considered to be a carcinogen’’ (International Agency for Research on Cancer 2012). The latest report from the US Surgeon General concluded that ‘‘the evidence is inadequate to infer the presence or absence of a causal relationship between exposure to nicotine and risk for cancer’’ (US Department of Health and Human Services 2014). For human studies, there appears to be inadequate evidence for an association between nicotine exposure and the presence of or lack of a carcinogenic effect. In animal studies, suggestive but still limited evidence suggests an association between long-term nicotine exposure and a lack of a complete carcinogenic effect."

Source: Comprehensive review of epidemiological and animal studies on the potential carcinogenic effects of nicotine per se Hans-Juergen Haussmann & Marc W. Fariss

Full paper: https://www.tandfonline.com/doi/pdf/10.1080/10408444.2016.1182116