Okay kiddo, so sometimes there are these tiny things inside our body called cells. And sometimes, these cells can start to grow and divide really fast and uncontrollably, which can cause something called cancer.
Now, a sarcoma is a type of cancer that starts in bones or soft tissues of the body, like muscles or tendons. It's called a sarcoma because it starts in something called mesenchymal cells, which are the cells that make up these tissues.
Sarcomas can be really scary, but doctors can use different treatments like surgery, chemotherapy, and radiation to try and get rid of the cancer. It's important to catch it early and get treated as soon as possible.
Remember, if you ever have any questions or concerns about your body, it's always okay to talk to a trusted grown-up or doctor.