A doctor once told her not to run. Now she’s taking on the Boston Marathon.

More than 10 years after surgery at Mass General Hospital for a giant cell tumor in her femur, she’s running Boston in support of the hospital that helped her get there.

Sydney Southern is running the 2026 Boston Marathon.

In our “Why I’m Running” series, Boston Marathon athletes share what’s inspiring them to make the 26.2-mile trek from Hopkinton to Boston. Looking for more race day content? Sign up for Boston.com’s pop-up Boston Marathon newsletter.

Name: Sydney Southern
Age: 33
From: Peabody

In 2014, I was diagnosed with a giant cell tumor in my femur. After surgery at Mass General Hospital, my doctor encouraged me to stick to low-impact activity. His exact words were, “You should only run if you’re being chased.” As a lifelong athlete with aspirations of one day running the Boston Marathon, this news was crushing.

Cambridge pediatric doctor running fifth Boston Marathon to support Mass General patients

After more than 10 years of careful monitoring, low-impact movement, strength training, and physical therapy, I’ve been fully cleared for all levels of activity, including running this marathon.

Running the Boston Marathon, something that once felt completely out of reach, is now a reality. It’s an opportunity and a privilege I don’t take lightly, and my journey here helps me carry gratitude and perspective with every step of training.

It only feels right to run and raise money for the place that restored my mobility, confidence, and ability to live an active life: Mass General Hospital.

I’m running for the patients and families who walk through MGH’s doors during some of the most uncertain and frightening moments of their lives, placing their trust in this hospital for the very best care. I’m running in support of the doctors, nurses, and staff who showed me extraordinary compassion, humanity, and skill, and who provide that same level of care to so many others day in and day out. I’m running for the countless patients, families, and friends whose lives have been touched by MGH, and for the impact this institution and its people have on so many.

I am so thankful for Mass General Hospital and incredibly proud to wear its name across my singlet on April 20th!

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