In 2016, osteosarcoma was the last thing on my mind. I was a typical and active high-school junior playing sports and hanging out with my friends. On a trip in December, I decided to try snowboarding for the first time, but it was harder than it looked and I kept falling. I had some pain in my leg and took over-the-counter pain relievers, assuming it was just a bruise from the falls.

In January, after playing in a flag football...