Cancer transmission between humans
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Human-to-Human Cancer Transmission: Overview and Mechanisms
Cancer is generally not considered a contagious disease, but rare cases of human-to-human cancer transmission have been documented under specific circumstances. These cases provide important insights into the biological barriers that usually prevent cancer cell spread between individuals and highlight the exceptional situations where these barriers can be bypassed Dujon2020Arakawa2024Greaves2018.
Cancer Transmission via Organ and Blood Transplants
One of the most recognized routes for cancer transmission between humans is through organ transplantation and, potentially, blood transfusion. Donor-derived cancer transmission can occur if a donor has an undiagnosed malignancy at the time of donation. Although the risk is very low—estimated at about 6 per 10,000 transplants—cases have been reported, especially when the donor’s cancer is only discovered after transplantation. Most transmissions involve aggressive cancers like lung cancer, and the risk is higher when screening protocols are less stringent Molodysky2021Nalesnik2022. Blood transfusions could theoretically transmit circulating tumor cells (CTCs) from donors with undiagnosed or dormant cancers, but this remains a hypothesis with limited direct evidence .
Maternal-Fetal and Perinatal Cancer Transmission
Rare cases of cancer transmission from mother to child have been documented, primarily during pregnancy or birth. The placenta can allow cancer cells to pass from mother to fetus, leading to maternal-to-fetal cancer transmission. Other scenarios include the transfer of preleukemic cells between monozygotic twins and the transmission of gestational choriocarcinoma. Additionally, there have been reports of infants developing cancer after aspirating maternal cancer cells during birth, particularly in cases of maternal cervical cancer. The child’s immune tolerance and the cancer’s ability to evade immune detection are key factors in these rare transmissions Arakawa2024Arakawa2021Greaves2018.
Barriers to Cancer Transmission Between Humans
Several biological barriers make cancer transmission between humans extremely rare. The main obstacles are the lack of a natural route for viable cancer cell transfer and the immune system’s ability to recognize and destroy foreign cells. Exceptions occur in situations where the immune system is suppressed (such as in organ transplant recipients) or where there is direct cell transfer (such as through the placenta or during birth) Dujon2020Arakawa2024Greaves2018.
Sexual and Vertical Transmission of Cancer-Associated Viruses
While direct cancer cell transmission is rare, certain viruses that can cause cancer, such as human papillomavirus (HPV), are commonly transmitted between humans through sexual contact and from mother to child. These viruses can lead to cancer development years after infection, but the transmission is of the virus, not cancer cells themselves .
Evolutionary Perspective and Rarity in Humans
Transmissible cancers are well-documented in some animal species, but in humans, natural cancer transmission is extremely rare due to strong immune barriers and the lack of regular cell transfer routes. Most documented cases in humans involve unique circumstances, such as transplantation, pregnancy, or severe immune suppression Dujon2020Arakawa2024Greaves2018.
Conclusion
Human-to-human cancer transmission is an exceptionally rare event, typically occurring only under special conditions such as organ transplantation, blood transfusion, or maternal-fetal transfer. The immune system and lack of direct cell transfer routes are major protective factors. Understanding these rare cases helps inform medical practice and highlights the importance of rigorous donor screening and monitoring in transplantation and transfusion medicine Dujon2020Molodysky2021Arakawa2024+3 MORE.
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