When my 11-year-old daughter, Averi, fell at school, we didn’t think anything of it. But when the bruise didn’t go away after several weeks, we got it checked out. Her pediatrician said it looked like a bunch of blood vessels because the bruise was right above the muscle. But she wanted to biopsy it to be sure.

On June 17, 2021, Averi’s doctors performed a needle biopsy and removed a mass on her hip half the size of a tennis ball...