Canine Transmissible Venereal Tumor

Canine transmissible venereal tumor (CTVT), also called transmissible venereal tumor (TVT), Canine transmissible venereal sarcoma (CTVS), Sticker tumor and infectious sarcoma is a histiocytic tumor of the dog and other canids that mainly affects the external genitalia, and is transmitted from animal to animal during copulation. It is one of only three known transmissible cancers; another is Devil facial tumor disease, a cancer which occurs in Tasmanian devils.

The tumor cells are themselves the infectious agents, and the tumors that form are not genetically related to the host dog. Although the genome of CTVT is derived from a canid (probably a dog, wolf or coyote), it is now essentially living as a unicellular, asexually reproducing (but sexually transmitted) pathogen. Sequence analysis of the genome suggests it diverged from canids over 6,000 years ago; possibly much earlier. However, the most recent common ancestor of extant tumors is more recent: it probably originated 200 to 2,500 years ago.

Canine TVT was initially described by Russian veterinarian M.A. Novinsky (1841–1914) in 1876, when he demonstrated that the tumor could be transplanted from one dog to another by infecting them with tumor cells.