Jon Kopaloff/Getty Images Hannah Brown
Brown, 27, shared in her book God Bless This Mess that she was diagnosed with the rare form of cancer in fifth grade, after struggling with unexplained and frequent stomachaches. An MRI of her stomach showed "a tumor the size of an egg" on her pancreas.
"They sent me for a biopsy, and a day or so later, my dad got a call with the results — not from our regular doctor, but from an oncologist," she recalled. "The tumor was malignant. Cancer. Pancreatic cancer — one of the deadliest forms of cancer there is."
According to the National Cancer Institute, solid pseudopapillary tumors of the pancreas are the most common form of pancreatic cancer in children and most often occurs in pre-teen girls. They typically are contained to the pancreas and do not spread, increasing the likelihood of recovery — which was the case for Brown.
Knowing that it hadn't spread outside of her pancreas made the process easier for Brown, she wrote, but she remembers her parents being extremely worried as she went into surgery.
"On the day of my surgery, I wasn't scared about what was going to happen to me. At all," she said. "Even though my mother was in tears and my dad looked as worried as I'd ever seen him in my life as the nurses came to wheel me into the operating room, I looked up at my mom from my hospital bed and said, 'Mama, I'm going to be okay.' "
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Brown said, though, that she was concerned about the possibility that she would need to undergo chemotherapy and radiation after the surgery if there were lingering cancer cells, because that meant she may lose her hair.
"There was a chance we'd have to go through radiation and chemotherapy, they said, depending on what the surgeon found once they got me into the operating room," she said. "But miraculously, I didn't need either one."
Hannah Brown's "God Bless This Mess"
And since the surgery, Brown has been cancer-free.
"I had to go to checkups a few times a year or so after that," she said, "but nothing else ever turned up in my scans or in my bloodwork."
Brown's memoir, which was released Tuesday, also covers her time on The Bachelor and The Bachelorette, her dating history and her struggles with disordered eating. She told PEOPLE in September that it's a story of "self-discovery."
"I feel so grateful for the opportunity to share my journey, including all the highs and lows, with those still figuring themselves out," she said. "I'm still learning and growing but hope that others can take away from my experiences and learn to embrace the messiness and beauty of life. I felt it was important to share my truth, honestly and without the opinion of others."