What if cancer could outlive its own host — jumping from body to body, spreading through bites, through mating, even through open water — and nobody noticed for thousands of years?

In this episode of Cold Cells, we open three case files on the most bizarre biological phenomenon most people have never heard of: transmissible cancer. We’re talking about a cancer in Tasmanian devils that spreads like a virus, a dog tumor that’s been alive for 11,000 years and has traveled every continent, and a clam leukemia that literally swims through the ocean to find its next victim.

This isn’t science fiction. All of it is real, all of it is happening right now, and the biology behind it — cell cycle breakdown, immune evasion, MHC class I, natural selection acting on a tumor like it’s its own organism — might be the key to understanding how our own  ...