[hughlomas]

I do not intend this as a contradiction but merely a tangential tidbit: Devil facial tumor disease [0] is an example of an actual, transmissible cancer in mammals, showing that it is at least possible.

[0] http://en.wikipedia.org/wiki/Devil_facial_tumour_disease

[adventured]

We also know that cancer can be spread / caused by virus, from one person to another (eg HPV, and there are probably others waiting to be discovered).

And we know that you can intentionally force the formation of tumors / cancer through introduction. We do this in mice as a regular course of study now.

I suspect that over the coming decades, we're going to find cancer is a far more communicable disease than previously thought.

[Dylan16807]

> spread / caused by

That seems like a giant conflation to me.

[karmajunkie]

HPV is also an oncovirus, responsible for cervical cancer and very likely many oral, throat, and esophageal cancers. And there's a vaccine for it.

[Edit: should be noted however that the vaccine is for the virus, not from the cancer that can arise from its infection.]

[dekhn]

Or oncogene transfection, which likely occurs in nature, not just the lab.