Cancer causes many deaths each year, and anyone that's lost someone to cancer knows how painful and grueling it can be. The one saving grace is that it ultimately only kills the host. But is this changing? According to several recent papers, scientists have suggested that cancer could become contagious. Cancer cells could have the ability to metastasize, not just from organ to organ, but from person to person. While this is not an imminent threat, it has already happened in unusual circumstances.