Mason Geertsen, a professional hockey player who recently joined the Buffalo Sabres, has spoken publicly about his experience with B-cell non-Hodgkin lymphoma. Geertsen’s diagnosis followed an injury during pregame warmups in November 2023 while playing for the Henderson Silver Knights, the AHL affiliate of the Vegas Golden Knights.
Initially, Geertsen believed he had suffered a knee injury, but further medical tests revealed abnormal bone marrow and raised suspicions of lymphoma. “That day was probably one of the worst of my life,” Geertsen said, recalling when he first learned of the possibility of cancer. His wife Clarity described the experience as surreal: “I feel like you can’t even take yourself back to that moment because you’re just trying to survive and get through it.”
After an initial benign biopsy complicated his diagnosis, Geertsen continued to play hockey until further scans confirmed B-cell non-Hodgkin lymphoma at a cancer center in California. Upon confirmation, Geertsen expressed relief at finally knowing what was wrong and focused on recovery. Clarity recounted her husband’s determination: “He just shifted into this superhero mindset. He was like, ‘I am never going to look at myself as weak. I am never going to look at myself as sick. I am just going to do what I can to take care of myself, take care of my body.’”
During treatment and recovery, Geertsen found support from his family and focused on small positive moments in daily life. The couple adopted a dog and watched comedies together to maintain morale.
In February 2025, they launched The Geertsen Opportunity Foundation to support others facing challenges similar to Mason’s. “Mason kind of held everybody together, which wasn’t even his job,” Clarity said. “Because he was the one going through it… There’s a purpose to this, and I just have to keep pushing through to see what it is.”
Geertsen underwent four rounds of targeted immunotherapy beginning in August 2024 while maintaining his training routine for hockey season. Treatment concluded in September; by November he announced he was in remission.
Although there is no cure for his type of lymphoma and regular monitoring is required, recent scans have shown no sign of disease progression.
This summer, The Geertsen Opportunity Foundation held its first free hockey camp in Drayton Valley, Alberta—Geertsen’s hometown—where Mason also visited Ryker, a local child recovering from stomach cancer.
Geertsen has since participated in hospital visits with teammates from the Buffalo Sabres at Roswell Park Comprehensive Cancer Center and intends to continue supporting others facing cancer diagnoses. “I know how hard it is,” he said. “I want to try and do as much as a I can to help as many people as I can in that situation. Just be that one positive thing that day, or that one win or uplifting moment they have that day.”
