OKLAHOMA CITY - When you meet Pierson, the first thing you notice is his warm smile.
But when Pierson was a toddler, his mother says she noticed something terribly wrong.
"I got him back from his dad and he looked seven months pregnant," Katy said.
She says panic set it right away.
"I'm running full tilt to grab my kid, and I stopped front and center and said, 'What's wrong with my kid?' And he said, 'Oh, he's just constipated," she remembered.
But Katy's motherly instincts told her it was something more so she got Pierson to a doctor as quickly as she could.
"Honestly, I think I was in shock. I really don't think I quite grasped the gravity of the situation," she said.
Then came the news that no family could ever prepare for; they were devastated to learn Pierson had a tumor in his stomach.
"He has a type of cancer called Rhabdomyosarcoma, there are about 350 patients diagnosed with this in the United States every year," said Dr. Ashley Baker, a member of the team of doctors treating the toddler.
Rhabdomyosarcoma attacks the muscles, so it makes Pierson incredibly weak.
However, he keeps on fighting, even after several relapses.
Hear more of Pierson's story on NewsChannel 4 at 5 p.m. on Monday.