The CDC's ToxFAQs page on Perfluoroalkyls [1] is one starting point, refer to the full 993-page report [2] for all the gritty details. Here's a high-level summary of the evidence on cancer risks:

> The International Agency for Research on Cancer (IARC 2017) concluded that PFOA is possibly carcinogenic to humans (Group 2B), and EPA (2016e, 2016f) concluded that there was suggestive evidence of the carcinogenic potential of PFOA and PFOS in humans. Increases in testicular and kidney cancer have been observed in highly exposed humans.

Less research on PFOS that aren't PFOA though, so there's room for dismissing the available evidence if you're so inclined.

[1] https://wwwn.cdc.gov/TSP/ToxFAQs/ToxFAQsDetails.aspx?faqid=1... [2] https://www.atsdr.cdc.gov/toxprofiles/tp200.pdf