Cancer as a contagious disease

In 2011, Hugo Chavez alleged that he was the victim of an assassination plot ... that unnamed US agents had infected him with a transmissible cancer. Scientifically speaking, that's highly unlikely. But what's interesting is that the idea of contagious cancer isn't totally outside the realm of reality. Transmissible cancers do exist, just not in any primate species. At Scientific American, Marissa Fessenden interviews a geneticist about the contagious cancers that affect dogs and Tasmanian devils.