# Similar: Why isn't cancer contagious? (Or IS it?) **URL:** \ **Category:** Factual Questions\ **Created:** [June 20, 2008, 11:11pm UTC](https://boards.straightdope.com/t/similar-why-isnt-cancer-contagious-or-is-it/453637 "2008-06-20T23:11:29Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![scrambledeggs](https://avatars.discourse-cdn.com/v4/letter/s/898d66/32.png) [@scrambledeggs](https://boards.straightdope.com/u/scrambledeggs)\ **Post date:** [June 20, 2008, 11:11pm UTC](https://boards.straightdope.com/t/similar-why-isnt-cancer-contagious-or-is-it/453637/1 "2008-06-20T23:11:29Z")
Ok second cancer one–Now that i figured out what it is, why can’t cancer be contagious? Or is it? If the cells just keep multiplying, if someone got injected somehow with someone else’s cancerous cells, would they not get cancer? Wouldn’t those alien cells keep multiplying? The immune system might kill it, but is that a certainty? And if injecting say, Henrietta Lacks’ cells into someone would give them cancer, what if a testube broke and the cancerous cells went into the air and people breathed them in? ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [June 20, 2008, 11:22pm UTC](https://boards.straightdope.com/t/similar-why-isnt-cancer-contagious-or-is-it/453637/2 "2008-06-20T23:22:18Z")
[Tasmanian Devils’ Existence Threatened By Rapidly Spreading Cancer](http://www.sciencedaily.com/releases/2008/01/080128173735.htm) > [@](#): > > A form of cancer has decimated the devil population by nearly 90 percent in certain geographical areas of Tasmania, and officials project that within twenty years the entire species could become extinct. ---
**Author:** ![JayRx1981](https://avatars.discourse-cdn.com/v4/letter/j/71e660/32.png) [@JayRx1981](https://boards.straightdope.com/u/JayRx1981)\ **Post date:** [June 20, 2008, 11:33pm UTC](https://boards.straightdope.com/t/similar-why-isnt-cancer-contagious-or-is-it/453637/3 "2008-06-20T23:33:14Z")
[QUOTE=scrambledeggs] Ok second cancer one–Now that i figured out what it is, why can’t cancer be contagious? Or is it? If the cells just keep multiplying, if someone got injected somehow with someone else’s cancerous cells, would they not get cancer? Wouldn’t those alien cells keep multiplying? [/quote] The simple answer is no because our genetic code produces a group of molecules on host cells called the major histocompatibility complex which allows ones immune system to differentiate host cells from non-host cells. Anything non-host can then be targeted by the immune system and killed off. > [@](#): > > The immune system might kill it, but is that a certainty? By and large, yes, it’s a certainty. There are certain factors that may allow someone else’s cancer cells to grow in a different host (transplant patients on lifelong immunosuppressants would be my best guess, or those immunocompromised due to loss of T-Cells), but those are relatively speaking fairly rare occurrences. > [@](#): > > And if injecting say, Henrietta Lacks’ cells into someone would give them cancer, what if a testube broke and the cancerous cells went into the air and people breathed them in? Airborne cancerous cells, assuming they could survive long enough, would still need a vector to get past the body’s natural barriers to entry–ie past the mucous membranes, layers of keratinized epithelium, etc. Bacteria and viruses have evolved such methods. Human cells haven’t. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [June 21, 2008, 12:00am UTC](https://boards.straightdope.com/t/similar-why-isnt-cancer-contagious-or-is-it/453637/4 "2008-06-21T00:00:58Z")
But, if you insert cancerous cells directly into the body, some cancers are transmissible: > **[Two Organ Recipients Die and Two Others Develop Cancer After Being Given...](https://jonathanturley.org/2008/04/08/two-organ-recipients-die-and-two-others-develop-cancer-after-being-given-cancer-victims-organs/)** > > Litigation is expected in a terrible tragedy developing over the use of cancerous organs mistakenly given to organ transplant patients who later died or developed cancer. The organs were harvested … ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [June 21, 2008, 12:43am UTC](https://boards.straightdope.com/t/similar-why-isnt-cancer-contagious-or-is-it/453637/5 "2008-06-21T00:43:06Z")
There’s also a form of canine venereal cancer that is transmissible: > **[Clonally transmissible cancer](https://en.wikipedia.org/wiki/Parasitic_cancer)** > > A transmissible cancer is a cancer cell or cluster of cancer cells that can be transferred between individuals without the involvement of an infectious agent, such as an oncovirus. The evolution of transmissible cancer has occurred naturally in other animal species, but human cancer transmission is rare. > In humans, a significant fraction of Kaposi's sarcoma occurring after transplantation may be due to tumorous outgrowth of donor cells. Although Kaposi's sarcoma is caused by a virus (Kaposi's sa... ---
**Author:** ![Bob55](https://avatars.discourse-cdn.com/v4/letter/b/e9c0ed/32.png) [@Bob55](https://boards.straightdope.com/u/Bob55)\ **Post date:** [June 21, 2008, 12:55am UTC](https://boards.straightdope.com/t/similar-why-isnt-cancer-contagious-or-is-it/453637/6 "2008-06-21T00:55:31Z")
[QUOTE=beowulff] But, if you insert cancerous cells directly into the body, some cancers are transmissible: > **[Two Organ Recipients Die and Two Others Develop Cancer After Being Given...](https://jonathanturley.org/2008/04/08/two-organ-recipients-die-and-two-others-develop-cancer-after-being-given-cancer-victims-organs/)** > > Litigation is expected in a terrible tragedy developing over the use of cancerous organs mistakenly given to organ transplant patients who later died or developed cancer. The organs were harvested … [/QUOTE] I’ve read about this before, I think someone got cancer from a kidney transplant. It is probable that they were on immunosuppressants which would allow for the cancer to spread into the new host more easily. ---
**Author:** ![Darryl\_Lict](https://avatars.discourse-cdn.com/v4/letter/d/7cd45c/32.png) [@Darryl\_Lict](https://boards.straightdope.com/u/Darryl_Lict)\ **Post date:** [June 21, 2008, 1:15am UTC](https://boards.straightdope.com/t/similar-why-isnt-cancer-contagious-or-is-it/453637/7 "2008-06-21T01:15:14Z")
Isn’t [cervical cancer](http://en.wikipedia.org/wiki/Cervical_cancer) generally associated with the human papillomavirus (HPV)? ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [June 21, 2008, 2:09am UTC](https://boards.straightdope.com/t/similar-why-isnt-cancer-contagious-or-is-it/453637/8 "2008-06-21T02:09:03Z")
This recent column by Cecil may be of interest: [Can dogs get venereal disease?](http://www.straightdope.com/columns/080516.html) > [@](#): > > The really sexy dog STD, though, is something called canine transmissible venereal tumor, a very rare example of what’s known as a parasitic cancer. Unlike most other contagious cancers such as cervical cancer in humans, CTVT isn’t spread by a virus but (as recently proved) by cancerous cells themselves. … It can be treated with surgery, radiation, and chemo, but most otherwise healthy dogs recover spontaneously after several months. > > Luckily for us, there are no known parasitic cancers in humans, and only two additional ones affect animals. One arose spontaneously in a laboratory hamster around 1960: it’s a reticulum-cell sarcoma that can be spread by casual contact, cannibalism (hamsters’ souls are a lot darker than you might think), and mosquito bites; the tumor grows in the larynx and eventually leads to suffocation. The other is a condition threatening Tasmanian devils with extinction in the wild, called devil facial-tumor disease. First noted in the 90s, it’s spread by bites; the tumors grow around the mouth and eventually cause death by starvation. ---
**Author:** ![Ferret\_Herder](https://avatars.discourse-cdn.com/v4/letter/f/e47774/32.png) [@Ferret\_Herder](https://boards.straightdope.com/u/Ferret_Herder)\ **Post date:** [June 21, 2008, 2:55am UTC](https://boards.straightdope.com/t/similar-why-isnt-cancer-contagious-or-is-it/453637/9 "2008-06-21T02:55:54Z")
[QUOTE=Darryl Lict] Isn’t [cervical cancer](http://en.wikipedia.org/wiki/Cervical_cancer) generally associated with the human papillomavirus (HPV)? [/QUOTE] Yes, though the transmitting host may never get cancer even if the recipient does, and not all HPV strains have the potential for causing cervical cancer. ---
**Author:** ![Spoke](https://avatars.discourse-cdn.com/v4/letter/s/a88e57/32.png) [@Spoke](https://boards.straightdope.com/u/Spoke)\ **Post date:** [June 21, 2008, 4:32am UTC](https://boards.straightdope.com/t/similar-why-isnt-cancer-contagious-or-is-it/453637/10 "2008-06-21T04:32:57Z")
[QUOTE=Darryl Lict] Isn’t [cervical cancer](http://en.wikipedia.org/wiki/Cervical_cancer) generally associated with the human papillomavirus (HPV)? [/QUOTE] …which has always made me wonder how many other cancers and chronic conditions might be caused by viruses of which we are simply unaware. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [June 21, 2008, 10:58am UTC](https://boards.straightdope.com/t/similar-why-isnt-cancer-contagious-or-is-it/453637/11 "2008-06-21T10:58:33Z")
Would cancer cells from one identical twin be able to take root in the other, for example during a transplant?