GIST — Gastrointestinal stromal tumor. To doctors, this is a rare tumor that is usually found in the stomach. To me, a 15-year-old girl, it is something that has changed my life in so many ways. Growing up, I was always a healthy girl. I never got the flu or even a cold. Whenever I even fell and scratched my knee, I would get right back up and put a Band-Aid on it.