Shared Placenta Transmits Rare Tumor
The case involves identical twin girls who shared a single placenta during pregnancy. During a magnetic resonance imaging scan at 33 weeks of gestation, doctors discovered a facial tumor on one of the fetuses. The twins were delivered at 34 weeks and subsequently diagnosed with undifferentiated sarcoma, a rare cancer that originates in tissues such as muscle and fat. The first twin died 12 days after birth, while the second twin passed away at nine weeks of age despite receiving chemotherapy treatment.
To determine whether the cancer developed independently in each child or spread from one to the other, researchers analyzed 33 DNA samples. This set included 23 normal and placental specimens alongside 10 tumor specimens. Using whole-genome sequencing, the team examined the complete genetic code and tracked underlying genetic variations.
While identical twins share nearly identical genetic material, developing cells accumulate distinct, minor genetic variations over time. By tracking these unique mutations, investigators discovered that genetic signatures originating in the first twin’s cells were present in the tumors of both children. This evidence led researchers to conclude that the cancer initiated in the first twin and traveled across placental blood vessels to the second twin.
Timeline of Intrauterine Cancer Transmission
Genetic analysis of accumulated mutations allowed the research team to construct a timeline of the disease’s progression. Investigators estimate that the initial cancer mutation occurred during the late first trimester of pregnancy. The transmission of the malignant cells from the first twin to the second twin through the vascular connection in the shared placenta likely occurred during the late second trimester.
Cancer is not a communicable disease and does not spread between individuals through ordinary daily contact. This event remains restricted to the unique vascular environment of a pregnancy where identical twins share a single placenta, where cancer cells moved through blood vessels to the other fetus. DNA comparisons between the twins and the placenta also revealed distinct distributions of early embryonic cells in both infants and placental tissue, pointing to a more complex embryonic splitting process than previously understood. Researchers note that because this finding stems from the analysis of a single pair of twins, additional study is necessary.
Twin Cancer Transmission Questions
Can cancer be transmitted during a normal pregnancy?
No. Cancer is not contagious. This documented transmission occurred because the identical twins shared a single placenta and interconnected blood vessels, allowing malignant cells to pass from one fetus to the other.
What type of cancer did the twins develop?
Both infants were diagnosed with undifferentiated sarcoma, a rare type of cancer affecting connective tissues such as muscle and fat, characterized by cells that lack the distinct features of normal tissue origin.
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