Nov. 28, 2013 -- Sarah Atwell always listened to her beloved grandmother, who taught her to love herself.
"My nanny always told us when we were sad to cheer us up, 'Be strong, no matter what happens,'" the 18-year-old told ABCNews.com.
But for Atwell, who lives with her family in Nova Scotia, that was a tough order. She was born with neurofibromatosis, which caused a massive tumor to grow on the side of her face.
Now, the story of her psychological and physical transformation, "The Girl With Half a Face," will air on Discovery Fit & Health on Dec. 18 at 10 p.m. (ET/PT), chronicling the weeks leading up to her successful surgery to remove the tumor.
According to the Mayo Clinic, neurofibromatosis is a genetic disorder that disturbs cell growth in the nervous system, causing tumors to form on nerve tissue. These tumors can develop anywhere, including the brain, spinal cord and nerves.
The tumors are usually benign but can sometimes become cancerous. Symptoms are often mild, but can include hearing loss, learning impairment and cardiovascular complications because of nerve compression caused by the tumors.
Atwell, like most with the disease, was diagnosed in early childhood at 8 months old. Since then, she has had headaches and blurred vision and eight different facial surgeries. But the biggest struggle has been facing the bullies at school.
"Sarah never noticed she was different -- she always thought she was the same as the other kids," said her mother, Tara Atwell, 44, who also has a milder form of the inheritable disease. "They didn't understand it was a tumor and thought it was some kind of horrible disease they could catch."
"I was in grade three and people were calling me names like 'fat face' and 'ugly' and were pushing me around," said Sarah. "They said I had a disease. Most of the time, I just walked away and didn't say much to them."
One day, a cashier at a store refused to accept Sarah's money because she thought she had a contagious disease.
But when she was 16, Sarah fought back, posting a YouTube video holding the sign: "Maybe one day the bullying will stop."
"I was tired of being bullied and I put in on Facebook," she said.
Her mother said she never realized the extent of the teasing until she saw that video.
Soon, the Discovery Channel ran across the compelling YouTube post and offered to make a TV documentary on Sarah's ordeal. Many surgeons had refused to tackle her tumor because of its complexity, but her plight caught the attention of the medical community.
Sarah had three surgeries in 2010 and a risky one to remove most of the tumor last year.
Now that surgery is complete, Sarah said, "It's pretty awesome. I am pretty sure most of it is gone except a little bit around the eyes. The doctor said he could not be sure if it would come back or not."
Today, she is a senior in high school and helps out as a teacher's aide. Sarah is excited about her future. "Hopefully," she said, "I will be working with kids."
Her mother echoed that optimism: "She can be anything she wants to be."
"If I could stand up to bullying, and if another kid who was bullied sees me and thinks they can talk to someone and think, 'I can stand up for myself,' then I have helped," said Sarah.
And her advice to others who may face bullying is the same as her nanny's advice to her: "Stand strong and don't let things get to you. Walk away and don't let them bug you."
Discovery Fit & Health is partnering with DoSomething.org, an organization for young people and social change. In an effort to get the word out about anti-bullying, DoSomething.org and the Wireless Foundation have created a campaign called Bully Text, a virtual text-based educational game in which users choose how to respond to bullies, whether the victim or a bystander, in typical situations at an imaginary high school. Learn more here.