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I came across of this question when I was cooking a beef dish the other day.

If the beef I used for cooking came from a cow that had cancer, and even worse, if part of the beef I used in a dish actually contained cancer cells, could consuming the dish increase my chances of getting cancer?

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For any reasonable risk, the answer is no. Virtually all tumors are non-transmissible under normal (non-laboratory) circumstances (three exceptions, discussed below, none in humans), so you could not possibly get the cancer the animal had.

However some cancers arise because of environmental factors which may still be present in the animal. For example, an animal exposed to polychlorinated biphenyls (PCBs) would be at a higher risk of developing cancer, and PCBs also tend to stay around in the animal for some time. It is at least possible that environmental exposure which gave the animal cancer is still around to increase the risk to you. In general, this is probably a pretty low risk from any one instance of eating a tumorous animal. However if you were to eat animals which were routinely contaminated with something carcinogenic, it could become a problem.

A similar story could be told about oncoviruses, that is viruses which can cause tumors or cancer. However all the oncoviruses known to date are restricted to humans. Further, if there were an hitherto unknown oncovirus which caused the tumor in the animal and still could cause an infection and neoplasm in humans, it would have to survive cooking and consumption. This route seems improbable.

The least probable route would be a directly transmissible tumor. There are two such tumors known: Tasmanian devil facial tumor disease and canine transmissible venereal tumor. A third variety was discovered this year (Metzger 2015), which is found in clams. None affects humans. Further, the chances of such a disease being able to transmit across species seems very improbable. Finally, food preparation is almost certain to kill off the tumor cells.

In summary, it is very improbable that eating an animal which had a neoplasm would pose any risk.

  • although I agree with the spirit of your answer, I disagree with the strong claims you make at the beginning. See for example en.wikipedia.org/wiki/Clonally_transmissible_cancer – rumtscho Oct 7 '15 at 14:51
  • Yes, thanks for the clarification. I should have said that those two are the only two known instances of transmissible tumors in the wild. There are a small number of additional cases where a tumor is transmissible in a laboratory setting, including newts, fish, mice, and hamsters. However these have never been observed in the wild (there's a short review with further reading in Murchison (2009)). – Hans Oct 10 '15 at 3:32
  • Serves me right for first responding then clicking the link. Apparently the a third transmissible tumor in the wild was discovered this year; I was unaware of it. Citation here. – Hans Oct 10 '15 at 3:39
  • Thank you for updating with more explanation on transmissible tumors. I knew that they exist (well, had to look it up to refresh my memory), but did not know enough detail to be aware that none of them affect humans. – rumtscho Oct 11 '15 at 10:20

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