AMS president Ed Clark said Scott died at her parents' home in the Atlanta suburb of Lilburn, where she had been undergoing hospice care.
Scott joined the speedway in 2005 after working for several teams and sponsors, her list of drivers including Matt Kenseth, Ricky Craven and Jeff Green.
"We will all miss her charisma, her penchant for detail and her way of making any task fun and enjoyable," Clark said in a statement. "To people throughout the NASCAR and the Atlanta media communities, she was a great friend and a consummate professional."
Scott was initially diagnosed with breast cancer in 2009 and underwent extensive treatment, including a dozen surgeries. She revealed on her blog that the disease had returned in her brain after she fell ill in late May while walking around the Jefferson Memorial during a vacation in Washington, D.C.
Scott underwent surgery a couple of weeks later to remove a dime-sized tumor on the right side of her brain, but never fully recovered.
"I've been meaning to write the final chapter about completing my journey, losing weight, getting healthier and getting my life back," she said on her blog. "Well I guess there was a reason I never wrote the final chapter as it looks as if this book (is) not closed."
In a June entry, Scott wrote of what she had learned during her fight with cancer.
"Planning is great, but waiting on things makes no sense to me now," she said. "Live each day with complete utter joy and let go of petty annoyances and disagreements is a great mantra. Let that be my gift to you — to love with every fiber of your being to all walks of life. Look for the good in people. It will astound you."
Around NASCAR, her death was mourned.
"Sad to hear Marcy Scott lost her battle with cancer," driver Kasey Kahne tweeted. "She was always the nicest lady. Always had a smile. Thoughts and prayers."
Hendrick Motorsports said on Twitter, "Our thoughts and prayers go out to the family and friends of Marcy Scott and (Atlanta Motor Speedway). She will be missed."
After learning Scott's cancer had returned, driver Joey Logano set up a fund to raise money for her care and treatment.
"Very sad to hear about Marcy Scott losing her battle with cancer," Logano tweeted Friday. "Was such a great part of our sport."
Survivors include her parents, Buck and Charlotte Scott, and her brother, Stewart Scott.
Funeral arrangements were pending.
Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.