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Human-to-human transmission of cancer? The answer is this

   Cancer is an incurable disease. People who have cancer have a high mortality rate and a low cure rate. Even if it is cured, there is a possibility of recurrence. Therefore, when people talk about cancer discoloration, they are also very concerned about whether the cancer is contagious.

  Since the last century, scientists have been searching for the answer to this question. A large number of facts have shown that cancer is generally not easily transmitted through daily life such as physical contact, sexual activity or sharing utensils. However, the world is full of surprises, and there are always exceptions to everything. In a very small number of rare cases, scientists have also discovered a terrible phenomenon-cancer cells can indeed be passed from one person to another, and grow and develop in the new body, causing cancer.

The tragedy of organ transplantation


  In 2007, a 53-year-old woman died of a stroke. She had signed a body donation agreement before her death. After her death, the doctor took out her healthy heart, lungs, liver and two kidneys, and then transplanted them to 5 people. Patients who need new organs. Before the transplant, the doctor conducted a detailed examination of the body of the organ donor and found no abnormalities. For the 5 patients undergoing transplantation, except for the failure of the heart disease patient's transplantation operation, the remaining 4 patients were successfully transplanted. They received new lungs, liver, left kidney and right kidney, and their bodies gradually recovered.

  However, the good times did not last long, and unexpected things appeared. The female patient who received a lung transplant was hospitalized because of physical discomfort 16 months after the operation. The doctor checked and found that she had breast cancer. Even more surprising is that the doctors found through DNA sequencing that the female patient’s breast cancer cells were not her own, but came from the 53-year-old organ donor. Obviously, during transplantation, breast cancer cells are hidden in the lungs of organ donors. These cells are transferred to female patients along with the lungs, and then grow malignantly and cause cancer. After another short year, the female patient who was infected with breast cancer died unfortunately.

  Female patients undergoing lung transplantation are not special cases. A few years later, three other patients undergoing organ transplantation also developed cancer. Two female patients who had their left kidney and liver transplanted died of breast cancer. The male patient who had their right kidney transplanted also detected metastatic breast cancer cells in their bodies. After discovering the tumor, the male patient chose to remove the transplanted kidney, stop the immunosuppressive drugs, and receive chemotherapy at the same time. Although his cancer is under control, he still needs a new kidney and can only wait for the second transplant opportunity.

Rare mother-to-child transmission


  The traditional view of the medical profession believes that women who have cancer during pregnancy will not pass the cancer to their unborn baby, because even if the cancer can cross the barrier of the placenta, it will be blocked by the baby's immune system. However, this traditional view has been subverted.

  In 2009, a 28-year-old Japanese mother suffered from cancer during pregnancy. She gave birth to a baby girl in the hospital. One month later, the mother had a heavy vaginal bleeding and was diagnosed with advanced leukemia and died. The baby girl was also diagnosed with leukemia when she was 11 months old.

  Scientists at the National Cancer Institute in the United States used genetic fingerprinting to study this case. They found that both mother and baby's cancer cells carry the same mutated cancer gene, but this gene is not inherited. Therefore, the infant's cancer cells are not self-generated, but can only be derived from the mother. Further examining the genes in infant cancer cells, scientists found that there was a "deletion mutation" in the cancer cell genes-a molecule called "human leukocyte antigen" was missing. The main function of this molecule is to distinguish each person's own cells from the cells of others. The lack of these molecules in cancer cells means that the baby's immune system cannot distinguish them as foreign cells.

  Therefore, in certain cancer cases, such as leukemia or melanoma, if the baby’s genes have "deletion mutations" that cannot identify destructive and aggressive cells, the cancer cells in the mother's body may cross the barriers of the placenta. It enters the developing fetus and successfully "falls to the ground". However, scientists pointed out that pregnant women with cancer have a very low chance of passing the cancer to their children-at present, only more than 30 such cases have been found worldwide.

Wound infections can also spread


  In the animal kingdom, cancer is often contagious. The most famous example is the Tasmanian devil.

  Tasmanian devil is a carnivorous mammal that only lives on the Australian island of Tasmania. They look like a cross between a mouse and a bear. They are not big and temperamental. They like to fight, and they like to bite each other's face, leaving scars. Tasmania has lived on Tasmania for 14,000 years, but since 1996, thousands of Tasmanians have started to develop tumors on their faces. This tumor is distributed on the face, head and neck of Tasmania. It is difficult for him to eat in his mouth and mouth.

  Most of the Tasmanian devil suffering from facial tumors will die, and the number has been reduced by 80%. With such a high mortality rate, is this cancer contagious? Scientists conducted genetic research on the Tasmanian devil with cancer, and found that the facial tumors of these Tasmanian devil only originated from two Tasmanian devil-a type of tumor called "DF T1" originated from the nerve membrane cells of a female Tasmanian devil. Spread to the entire island; another type of "DFT2" tumor originated from a male Tasmanian devil and spread mainly in the southeastern region of Tasmania.

  Scientists speculate that because the Tasmanian devil is often torn, its facial tumor cells often fall into the other's facial wounds, and because of the long-term isolation on an isolated island, most of the Tasmanian devil are related, and their immunity is very similar. , So that the tumor cells that the own immune system cannot fight against will naturally not be destroyed by the opponent's immune system. Therefore, during a fight, the facial tumor of one individual can spread to the next individual through the wound, so that a large-scale outbreak of cancer becomes a "mass plague."

  There have also been cases of cancer spreading in wounds in humans. In the 1990s, a 53-year-old surgeon performed an abdominal tumor resection on a 32-year-old patient. When performing this operation, the surgeon accidentally cut his own hand, and he immediately disinfected the wound. Despite this, five months later, a tumor grew on the injured part of the surgeon's hand. When the tumor was removed and analyzed, it was found to be composed of cancer cells from the 32-year-old patient.



  In addition, through wounds, sometimes cancer cells can even spread from animals to humans. In 1986, a laboratory technician accidentally poked an injection needle into his hand while injecting colon cancer cells into a mouse. A few weeks later, a tumor grew in the poked area, but fortunately it was successfully removed.

Don't worry too much



  Although cancer cells can be passed from one person to another, people do not need to worry too much.

  Scientists point out that under normal circumstances, cancer does not spread from person to person. On the one hand, cancer cells are very fragile outside the body and difficult to survive, so they are not highly infectious. On the other hand, if you think about it, you will find that the above cases of human beings infected with cancer are very rare. Only the case of organ transplantation requires a high degree of vigilance-because patients who have received organ transplantation, in order to solve the rejection reaction, they often take immunosuppression. Drugs, this will give cancer cells a chance to take advantage of. Therefore, before organ transplantation, doctors should strictly monitor the physical condition of the organ donor to prevent the tragedy of cancer infection from happening again.

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