10-Year-Old Boy Donates Stem Cells To Father Fighting Cancer
MONDAY, Sept. 22, 2025 — A Los Angeles-area dad is surviving leukemia thanks to his 10-year-old son, who earlier this year became the youngest-ever stem cell donor at Cedars-Sinai Medical Center.
Stephen Mondek’s donation provided a brand-new immune system for his father, Dr. Nick Mondek, who has been battling acute myeloid leukemia.
Nick made it home from treatment on Aug. 16, in time to see the final inning of Stephen’s Little League game.
“I felt good helping my dad, and it felt good to have him home,” Stephen said in a news release.
“A donation from a child this young is very rare,” Dr. Hoyoung Chung, a critical care pediatrician at Cedars-Sinai Guerin Children’s, said in a news release. “Stephen was very brave, and our team made sure everything went perfectly so that this young boy could help his father.”
Nick Mondek, an anesthesiologist, was first diagnosed with leukemia in 2022.
A stem cell transplant from his brother sent him into remission, but Mondek’s cancer returned in April this year.
“We followed every clinical protocol but the disease still managed to come back, so we had a new problem on our hands,” Dr. Ronald Paquette, clinical director of the Stem Cell and Bone Marrow Transplant Program at Cedars-Sinai Cancer. “How could we treat his cancer a second time around and have a better chance that it doesn’t return?”
A search among Mondek’s relatives and the National Bone Marrow Registry failed to turn up a match. It was then that Mondek recalled a close friend with lymphoma who’d received a transplant from his 18-year-old son.
“How young could you go with a donor?” Mondek asked Paquette.
Paquette said Stephen would need to be tested to make sure his immune system was compatible with his father’s, but that the genetics from his son’s donation might actually prove better for fighting leukemia than the perfectly matched stem cells Mondek got from his brother.
Kids receive half their DNA from their parents, so Stephen would be half-matched to Mondek. A half-matched immune system might more easily recognize and kill blood cancer cells, Paquette said.
After several weeks of pre-donation prep, Stephen went to Cedars-Sinai’s pediatric intensive care unit in July for the donation. He was placed under anesthesia for about an hour while doctors inserted a catheter into a vein in his neck.
Then Stephen spent six hours in a hospital bed while his blood cycled through a centrifuge that separated out the stem cells.
“Being an anesthesiologist, I put people to sleep every day, so I reassured myself that everyone wakes up when they go to sleep under anesthesia,” Mondek said. “But during the whole process that I've gone through, those 60 minutes when Stephen was asleep were probably the toughest.”
A week later, Mondek received the collected stem cells, after undergoing six days of chemo to clear out his immune system and make it more likely his body wouldn’t reject Stephen’s donation.
“Transplant day is always dramatic,” Paquette said. “The patient knows that they cannot survive without the stem cells, and the delivery of the stem cells into their body is like a rebirth. We call that day their stem cell birthday.”
Mondek spent two more weeks in the hospital to protect the reborn immune system he got from his son.
It could be a year or more before docs know for certain whether the donation will help Mondek beat his leukemia, Paquette said.
But Mondek is optimistic that his son’s donation will prove life-saving.
“Everything lined up for this,” Mondek said. “Dr. Paquette said the perfect donor for me would be someone who's young and healthy and a 50% match, and we found him. He was right here in front of us.”
Sources
- Cedars-Sinai Medical Center, news release, Sept. 16, 2025
Disclaimer: Statistical data in medical articles provide general trends and do not pertain to individuals. Individual factors can vary greatly. Always seek personalized medical advice for individual healthcare decisions.
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