If a cancerous cell enters the body of a healthy person from someone else's blood or something, will that healthy person get cancer? In human beings.
1$\begingroup$ Yes it can. See livescience.com/… $\endgroup$– steridNov 8, 2018 at 11:54
2$\begingroup$ @sterid those case involve immunosuppressed patients with end organ failure. This question is about what happens when a healthy person is exposed to cancerous cells $\endgroup$– De NovoNov 8, 2018 at 14:11
Can a cancer cells from someone else's body cause cancer in a healthy person?
No. Cancer cells from another person cannot cause cancer in a healthy person. The rare cases of transmissible tumors all involve unhealthy or not yet developed persons.
Transmission of tumor cells from one individual to another happens, but is quite rare, and in all cases involves some compromise or reduced development of the immune system. Though tumor cells do metastasize in an individual, when this occurs, tumor seeds must be able to evade the immune system and find an environment suitable for adhesion and replication. Tumor associated cells (non cancerous cells that regulate the microenvironment to make it favorable for growth and replication) are discussed in this seminal paper on cancer biology by Hannahan and Weinberg. There are similarities to infectious processes, but cancer is not measles. Tumor cells don't shed in comparable numbers, aren't adapted for immune escape in a separate host, and don't express appropriate adhesion proteins for portals of entry on a new host or readily induce tumor associated niches in a new host. The cases where person-to-person transmission of cancer via tumor cell inoculation does occur seem to demonstrate more how cancer cells are not infectious agents.
Donor-related tumors in transplant patients occur in immunosuppressed patients, but are still rare. The low frequency of transmission seems to be due, in part, to screening. The fact that we see this at all demonstrates the significance of transmission route and immune escape.
Maternal-fetal, and in utero twin-twin seem to be exceedingly rare, but have occurred, again, demonstrating the existence, but poor efficiency of transmission. Here, the fetus has an undeveloped immune system. I would not consider this case to be cancer cells causing cancer in a healthy person.
Inoculation of volunteers with tumor cells in a problematic series of experiments at Sloan Kettering in the 50s, transplantation of tumor cells into patients with other cancers, resulted in growth, recurrence after excision, and death in some cases. Transplantation into healthy volunteers (yes, they did this) resulted in nodules that spontaneously regressed. This experiment has since been interpreted as evidence for immune system control of transplanted tumor system in healthy individuals, as compared to growth and progression in a receptive niche in a cancer patient.
So person-to-person transmission of cancer cells is rare and requires an immunosuppressed or undeveloped host, or a host who already has cancer. There are no documented cases of person-to-person transmission to a healthy individual, and documented cases of failed transmission despite a surgical attempt. This is because, unlike an infectious microbe, in a healthy individual, there is not a suitable receptor for adhesion at an exposed or accessible site, a suitable environment for replication, and adaptations for immune escape by tumor cells in the original host are not effective in a new host.
As a side note, there are contagious cancers in other species, but this doesn't seem to be particularly relevant to a question about whether cancer can be transmitted between two humans. Many cancers have transmissible risk factors (e.g., human herpesvirus-8, hepatitis B and C viruses, human papilloma virus 16 and 18, and others)
$\begingroup$ @Chris I don't believe I have that privilege (moving other people's comments to chat). Feel free to move the whole series of comments to chat if you think they belong there. $\endgroup$ Nov 8, 2018 at 18:04
$\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$– Chris ♦Nov 8, 2018 at 18:05
$\begingroup$ I thought about you guys moving to chat. Anyway, the chat link is above. $\endgroup$– Chris ♦Nov 8, 2018 at 18:07
1$\begingroup$ The last sentence in this answer seems to refute the others. If the introduced cancer cell contains a cancer-causing virus then the answer is 'yes', my cancer cell could give you cancer. $\endgroup$– amINov 8, 2018 at 21:26
2$\begingroup$ @aml good instinct, but that doesn't happen to be the way it works. The virus is the risk factor, not the cancer. If you want to ask a separate question about that, I'd be happy to answer in detail. I'll just give you an example here: blood exposure could, for example, expose someone to HBV, and they might develop cancer 30 years later, but it would be the extracellular HBV, not any cancerous cell that was responsible. The foreign cancerous cell would be rapidly killed by the healthy host's immune system. $\endgroup$ Nov 8, 2018 at 21:59
Before OP edited his/her question, it was a little unclear whether the question was only about humans. The following answer is more general than asked as it also considers cancers in non-humans
Most cancers are not transmissible but some are. We call them (clonally) transmissible cancers.
The most famous case of transmissible cancer is the Devil facial tumour disease in Tazmanian devils. Other cases of transmissible cancers exist in Syrian hamsters, dogs (CTVT), and some bivalves. No such transmissible cancer is known to exist in humans.
Transmission of viruses inducing cancers
There are cases of cancer caused by viruses. Those viruses are transmissible and hence it looks like the cancer itself is transmissible. In humans, this is for example the case of Kaposi's sarcoma-associated herpesvirus.
Transmission via transplant
Finally, there are cases of cancer that can be transmitted to a new person via a tissue transplant. In humans, Kaposi's sarcoma is (again) an example.
$\begingroup$ Kaposi's sarcoma is not a transmissible cancer. It has a transmissible risk factor, HHV-8, but this is definitely not an example of cancer cells from one person causing cancer in another person. The cancer cells are not the transmissible agent (unlike the transmissible cancers in nonhuman animals). The special cases of Kaposi sarcoma transmission after transplant definitely don't involve healthy recipients. These patients are immunosuppressed, and the cells are, well, transplanted. $\endgroup$ Nov 7, 2018 at 14:39
$\begingroup$ @DeNovo You're right. I actually made reference to transmission of Kaposi's sarcoma indirectly via the transmission of a herpesvirus. I clarified that. Thanks. I added the idea of transmission via transplant. If I am not mistaken Kaposi's sarcoma is known to be "transmissible" via both transplant and virus transmission. Please correct me if I am wrong. $\endgroup$– Remi.bNov 7, 2018 at 15:02
$\begingroup$ Thanks for editing. I'm removing the downvote. I'm not going to upvote because I don't think this directly addresses the question about what happens when cancerous cells enter the body of a healthy person. $\endgroup$ Nov 7, 2018 at 15:08
$\begingroup$ The answer states that different cancer types may be transmissible but I think this is wrong, or at the very least misleading. In reality the transmissibility mostly isn't a function of the cancer, it's a function of the host organism. Tasmanien devils have transmissible cancer due to a recent population bottleneck that reduced genetic (and thus immune factor) diversity. Same for transmissible dog cancer cases. $\endgroup$ Nov 7, 2018 at 23:12
3$\begingroup$ @KonradRudolph both the immune characteristics of the animal and the cellular behavior and genetic characteristics of the neoplasm are important here. I think it is correct to say that only a few types of cancers are transmissible. Tasmanian devils have a wide variety of neoplasms, but only DFT is transmissible. $\endgroup$ Nov 8, 2018 at 1:48
The answer is no.
From molecular/mechanistic point of view cancer cell itself is not a self-maintaining and independent creature. Even assuming its infinite potential to renew and grow, it still needs constant nutrients supply and tailored microenvironment to survive. Therefore, there is a growing number of attempts to therapeutically target tumour cells niche, see: Joyce JA, Cancer Cell, 7(6), P513-520, 2005 and Belli C. et al., Cancer Treat Rev. 2018 Apr;65:22-32. To overcome this limitations, Cells can undergo epithelial-mesenchymal transition, which allows for migration outside the primary location and is crucial to initiate metastases.
Another important issue is the major histocompatibility complex, which allows to identify and eliminate cells, that contains foreign antigenes. Also, constant immune surveillance in immunocompetent individuals leads to elimination of potential cancerogenous cells. Therefore, patients with immunodeficiencies (eg. with AIDS or on prolonged pharmacological immunosuppression) have significantly higher risk of developing infection-related cancers, such as cervical cancer (HPV) or Kaposi Sarcoma (HHV-8).