One type of cancer in domestic dogs was possibly passed down from wolves;
[link
http://www.sciencedaily.com/releases/2006/08/060811075902.htm]http://www.sciencedaily.com/releases/2006/08/060811075902.htm[/link];
"A type of cancer that affects dogs throughout the world is in fact a sexually transmitted disease that originated from a single source, according to research by a UCL team published in the journal Cell.
Canine transmissible venereal tumour (CTVT) is unique because the cells of the tumour itself are transmitted during sex. Dr Claudio Murgia, UCL Immunology & Molecular. Pathology, studied tumours taken from 16 dogs in Italy, India and Kenya. He found that the DNA of the tumours was not the same as the DNA of the dogs – in other words, the tumours had come from outside the dogs#%92 bodies. A further analysis of 40 tumours archived in vet labs in five continents showed that the tumours were genetically almost identical and demonstrated that CTVT originally came from a single source.
Comparison of the tumour DNA with that different of different dog breeds, conducted with geneticists and computer experts in Chicago showed that the culprit is likely to have been a wolf or ‘old#%92 Asian dog breed from China or Siberia, such as a Husky or Shih Tzu. By counting the mutations in the DNA, the team also concluded that the dog lived between 250 and 1000 years ago."
The article also mentions a type of cancer that has recently been found in Tasmanian Devils which is transmitted by biting.