‘Canine transmissible venereal tumour’ (CTVT) is a cancer that spreads between dogs through the transfer of living cancer cells, primarily during mating. The disease usually manifests as genital tumours in both male and female domestic dogs. The cancer first arose approximately 11,000 years ago from the cells of one individual dog; remarkably, it survived beyond the death of this original dog by spreading to new dogs. The cancer is now found in dog populations worldwide, and is the oldest and most prolific cancer lineage known in nature. Read more..