The Sabres forward privately battled non-Hodgkin lymphoma in 2023 and 2024.
Mason Geertsen spent the days and months following his cancer diagnosis looking for small wins, in whatever form they came.
A laugh during an Adam Sandler comedy. Morning cups of coffee with his wife, Clarity.
These are the moments Mason lived for while he braved a year of uncertainty.
“The biggest thing for what I was trying to do at that point in time, was not dwell,” Mason recalls, nearly two years removed from the freak accident that put him on a path to recovery.
“Obviously, accept it, where I’m at. But not let it eat me alive. Some days, you lose. But hopefully you win more than you lose.”
Mason – with the support of Clarity along with his parents and two sisters – balanced life as a professional hockey player and treatment for B-cell non-Hodgkin lymphoma entirely out of the public eye. It wasn’t until last November, after he had made it to remission, that the family went public with his battle.
Now, Mason is sharing his story as he settles into a new home with the Sabres, hoping to use his platform as a source of inspiration.
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Mason signed with Buffalo this past summer with 64 professional fights on his resume. The 30-year-old has made a career out of answering the bell in defense of teammates.
His toughest fight began in pregame warmups on a November night in Henderson, Nevada.
Mason was preparing to play a game for the Silver Knights, the AHL affiliate of the Vegas Golden Knights. He slipped on a puck, causing discomfort in his knee. He ignored the pain and played that night against the Tucson Roadrunners. He played again the following day and fought 6-foot-9 Tucson enforcer Curtis Douglas.
Mason finally relented to the pain and went in for an MRI on Monday, Nov. 27, 2023.
“That day,” he says, “was probably one of the worst of my life.”
Mason went for an MRI on his knee that morning. He was home with Clarity when he received a call from the team medical staff.
Can you come back? We need to do another scan.
Mason and Clarity feared a serious injury to his knee. He returned for an X-ray, after which he was told to meet with the Golden Knights’ team doctor. The urgency – at this point, it was past 6 p.m. – stirred thoughts of a potential surgery.
Neither Mason nor Clarity expected the answer that awaited them.
Your bone marrow is not normal and we think it could be lymphoma.
The doctor told Mason that, because lymphoma can weaken bones, it was unlikely he would ever play hockey again.
Stunned and in denial, Mason and Clarity drove at 9 p.m. to downtown Vegas for bloodwork, their future suddenly uncertain.
“It was just surreal,” Clarity recalled. “I feel like you can’t even take yourself back to that moment because you’re just trying to survive and get through it.”
That initial round of tests was followed by a small biopsy in early December on Mason’s shin, which only complicated the matter. The results were benign, leaving doctors to wonder if the issue was an autoimmune disease rather than cancer.
Mason returned to the ice on Dec. 22, less than a month after being told he would never play again. He finished out the season with Henderson, resuming his role as defenseman and enforcer while fans, media and opponents remained unaware of the lingering battle in the back of his mind: He was sick, but without symptoms and without answers.
Further scans upon the conclusion of Henderson’s season revealed the condition had worsened significantly. Mason was sent to a cancer center in California for an extensive biopsy, where doctors drilled into his femur and removed three samples of bone marrow.
This time, finally, the initial diagnosis was confirmed: B-cell non-Hodgkin lymphoma.
Clarity fought back tears when she met her husband after the surgery. Mason, still disoriented from the anesthesia, smiled and laughed.
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Mason saw his diagnosis, in a sense, as a form of relief. He finally knew what was wrong; now his focus could turn toward fixing it.
“He just shifted into this superhero mindset,” Clarity recalled. “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 the months of uncertainty and subsequent months of recovery, Mason refused to use the word “cancer.” He surrounded himself with family, who traveled to visit frequently from Alberta, and took note of the small wins in daily life.
Mason and Clarity watched movies – only comedies, nothing sad or scary. (Adam Sandler’s entire filmography was heavy in the rotation.) They cherished routine tasks like trips to the grocery store. They fostered a dog, Tilly, then adopted her.
Post-retirement plans to start a non-profit organization were expedited. The Geertsen Opportunity Foundation was launched in February 2025.
“Mason kind of held everybody together, which wasn’t even his job,” Clarity said. “Because he was the one going through it. But just who he is as a person, he was like, ‘I’m not going to let this define me. There’s a purpose to this, and I just have to keep pushing through to see what it is.’”
Treatment began in August 2024, weeks before the start of the hockey season. The plan was for Mason to undergo four rounds of targeted immunotherapy. There were no promises made, no percentages of success; they could only perform the treatment and see how his cancer responded. The first treatment was a seven-hour day, four of which were spent in a chair, hooked up to an IV. It was as exhausting mentally as it was physically.
Mason’s schedule in the weeks leading up to training camp was as follows: working out Monday through Thursday, cancer treatment on Friday, recovery on Saturday and Sunday.
Treatment concluded on Sept. 14. He was present for the start of camp two days later, his battle still a secret to the public.
“One thing about Mason is he is never going to give up,” Clarity said. “He felt so horrible during these treatments and he still fought through and made sure to keep up a routine. It was hard to get him to rest.”
The treatment was successful. In November of last year, amid Hockey Fights Cancer month, Mason released a statement regarding his fight with cancer. He was in remission.
Mason Geertsen shares his journey
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There is no cure for Mason’s lymphoma. He is in remission thanks to his treatment but must stay vigilant should his cancer ever return. He had a clean scan in January and another in April. He’s due for his next scan in the coming weeks at Roswell Park.
He and Clarity continue to live in the moment, even now that they’ve made it through the thick of their battle.
“We were actually talking about this the other day,” Clarity said. “We were both like, these two years feel like we’ve kind of been given a new lease on life because we’ve been able to breathe a little bit. Our life is so full because it’s made up of us appreciating all the small moments.
“I don’t take any second that I have with Mason for granted because obviously there was a point in time where I didn’t know if I’d have years left or I’d have months left.”
The Geertsen Opportunity Foundation held its first completely free hockey camp this past summer in Mason’s hometown of Drayton Valley, Alberta. While in town, they visited a local child, Ryker, who had battled stomach cancer. Mason and Ryker bonded over their shared experience.
It was the sort of interaction that inspired Mason to make his cancer public in the first place.
Mason recently joined teammates on the Sabres’ annual visit to Roswell Park. He had done hospital visits throughout his career; now, the emotions hit him differently. He’s been through the bad days.
He plans to make a habit of visiting Roswell regularly.
“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.”
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