Searcher- Is Cancer Contagious?

Recently Hugo Chavez died of an unknown (at least to us) form of cancer.  Before he died, he blamed the United States for giving him cancer by insinuating that we had the technology to infect people with cancer.  This is of course not true, but it does bring up the question of can cancers be contagious?  The answer is yes.

In some non human species, such as dogs and Tasmanian devils, animals can infect each other with cancer.  Essentially Tasmanian devils are nasty and fight well.  They rip up each other's jaws and if one has cancer in its jaw caused by facial tumor disease, then some of the cancerous cells from its jaw may be able to transplant themselves into the ripped up jaw of the opposing Tasmanian devil.  Since there is very limited genetic diversity amongst that species, the cells go unnoticed and multiply, eventually killing the creature. The cells are unnoticed because the cancer cells are so similar to the other cells in the devil's body that the immune system does not identify it as foreign and mount an attack.  Even when faced with some genetic diversity, the cells have discovered how to produced fewer cell markers that would identify it as a threat to the immune system.  Dogs are very similar, however their's is a sexually transmitted disease called canine transmissible venereal tumor.

So why haven't we heard of this occurring in humans?  Essentially because there is so much genetic diversity amongst our species that it is harder for a cell to fly under the radar because our cells have a wider diversity of cell markers.  There have however been cases.  For instance, a mother can transmit melanoma to her fetus and people getting organ transplant can get cancer from the donor.  In the case of transplant, the donor already had undetected cancer and the recipient is generally on immunosupressants so the immune system is unable to recognize the threat.  In short, cancer can be contagious, however not in the same sense that viruses are contagious.  Hugo Chavez was not zapped with a cancer beam, he simply got cancer.

http://www.scientificamerican.com/article.cfm?id=is-cancer-contagious