Is cancer contagious?

This is an automatically translated article.

Posted by Specialist Doctor I Le Thi Nha Hien - Department of Medical Examination & Internal Medicine - Vinmec Nha Trang International Hospital

1. Is cancer contagious?

According to research results, papillomavirus (HPV) causes cervical cancer in women, genital warts and anal cancer in men. In addition, environmental causes such as cigarette smoke and radiation exposure can also cause cancer in humans. However, to date, there has not been any clear evidence that cancer is naturally transmitted from person to person through contact.
For animals, several studies have been done and shown that cancer can be contagious in dogs. It's a sexually transmitted disease called canine transmissible venereal tumor (CT VT) or Tasmanian devil face tumor. These cancers can cause large sores in the dog's mouth and around the jaw. When they bite other animals, cancer cells spread through the wound and cause disease. In both Tasmanian disease and CTVT, tumors have evolved in populations of truly inbreeding animals. There is a lack of diversity and, therefore, the cancer is genetically very similar to the animals it transmits.

2. Why does a lack of diversity help cancer spread in animals?

Cancer is transmitted to animals that are both genetically and tumour-like. The immune system does not "see" it and does not produce an immune response. The cancer can then grow until the animal is killed.
Over time, the devil's facial tumor has encountered animals that are genetically distinct from it. But cancer has found a way to down-regulate (or under-produce) cell surface molecules, which are considered red flags for the immune system in different animals. genetic. These flags are part of the major histocompatibility complex (a set of molecules that are attached to cells to regulate interactions with immune cells) - they are MHC molecules. Without those special immune molecules, cancer could fly under the immune system's radar and spread from animal to animal

3. What foreign cells does the immune system monitor?

Cancer is caused only by mutations in cells. The human immune system is still patrolling and looking for those cancer cells. If the human immune system sees a cell as cancerous, it kills it. Therefore, cancer can arise often, but people do not really know about them.

4. Why is cancer not contagious and grows in humans?

Cancers that are non-communicable and develop in humans can be attributed to genetic diversity. In a population with a lot of genetic diversity, everyone has very different versions. So, if a cell enters the body and has a different flag combination, the immune system destroys it.
The reason family members are needed for an organ transplant is because they are more likely to share similar symptoms (making the transplanted organ more likely to be tolerated by the immune system) . However, there will be some variation in the combination of these cell surface flags that they have, which is why transplant recipients are often given immunosuppressive drugs.

5. In what cases can cancer be transmitted from person to person?

The mother can pass the cancer on to her unborn baby (for example, melanom has been passed from mother to fetus). Also, during an organ transplant, if the donor has cancer, it is possible to transmit the cancer that way.
In fact, someone may not even realize that they have a small melanoma that has metastasized and spread to an organ. When they transplant that organ, the recipient will also develop melanoma.

6. Is it possible to get cancer from a blood transfusion?

That can happen if blood cancer cells are present during the transfusion. But often, cancer cells look foreign to the body's own cells, so it's very likely that the immune system will react.
However, if the cancer could be invisible to the immune system (because it is genetically similar to the body's cells or the cancer has been modified or grown in some way) leaving the immune system unnoticed) cancer can develop in the recipient.
In the case of organ transplant recipients, who are being immunosuppressed to help the body accept the new organ, receive a blood transfusion, cancer is more likely to occur.

7. Does injecting someone with cancer cells give them cancer?

There have been cases where surgeons have made cuts during surgery and developed cancer at the site of the cut. In this case, perhaps the cancer cells found a way into the surgeon's skin and started to grow.
However, the body cannot catch cancer easily. These cases are very rare. There have been cases in the literature where cancer has been intentionally transmitted between people, but it was a situation where they were close relatives. Otherwise, the immune system will destroy the foreign cell.

8. Is there a risk of infection by contact with potentially cancerous objects?

There is a possibility of this happening, for example, viruses can cause cancer. If you can be sure that a person has contracted a cancer-causing virus, that person can develop cancer. The same is true for radiation, asbestos or other carcinogens.
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References: Marissa Fessenden- Scientific American