A major investigation has revealed that a sperm donor, unknowingly carrying a genetic mutation linked to a significantly increased cancer risk, fathered at least 197 children in various European countries, including Greece. Alarmingly, some of these children have already passed away.

According to experts who spoke with the BBC, only a small fraction of the children who inherited this mutation are expected to avoid developing cancer during their lifetime. The sperm was donated to the European Sperm Bank in Denmark.

The donor, an anonymous man who began donating sperm in 2005 while a student, had passed standard screening procedures. However, his sperm carried a mutation in the TP53 gene—a crucial gene responsible for preventing cells from becoming cancerous. While most of the donor’s body does not carry the harmful mutation, up to 20% of his sperm cells do. Children conceived from this affected sperm inherit the mutation in every cell, a condition known as Li-Fraumeni syndrome, which carries up to a 90% risk of developing cancer, often in childhood, and breast cancer later in life.

The Danish European Sperm Bank expressed deep sympathy for the affected families and admitted that the sperm had been used extensively in certain countries, including Greece.

The case came to light when doctors treating children with cancer linked to sperm donation raised concerns with the European Society of Human Genetics. At least 23 children with the mutation were identified among 67 known cases at the time, with ten already diagnosed with cancer.

“The investigation found that the total number of children born from this donor is at least 197, though this may not be the final figure as data from all countries has not been collected,” the BBC reported. It remains unknown how many of these children inherited the dangerous mutation.

Cancer geneticist Dr. Edwin Kasper from Rouen University Hospital, who presented the initial findings, revealed, “We have many children who have already developed cancer. Some have developed two different types of cancer, and sadly, a few have died at a very young age.”

The BBC also highlighted the story of Céline, a single mother in France whose daughter was conceived using the donor’s sperm 14 years ago and carries the mutation. Céline received a call from the fertility clinic in Belgium advising her to test her daughter. She expressed no ill will towards the donor but condemned the fact that she was given sperm that was not “clean or safe” and posed a risk.

“We don’t know when, who, or how many will develop cancer. I understand the high probability, and when it happens, we will fight, and if many cases arise, we will fight many times,” she said.

The European Sperm Bank clarified that neither the donor nor his family are ill and that such mutations cannot currently be detected through routine genetic screening. They immediately excluded the donor once the issue was discovered.