The risk in cannibalism is around prion diseases, which is mostly a problem when we ingest brain tissue. Both mad cow disease (bovine spongiform encephalopathy) and kuru (a close human analogue) are more problematic when infected brain tissue is on the menu.

With mad cow, the cattle were fed from recycled parts of the same species, mostly organ meats (including the brain). With kuru, the prions propagate mostly through brain tissue. Those prions sometimes find their way into muscle tissue, but unless we seed the lab-grown meat with proteins which include prions, it's unlikely to be an issue.