Sarcoma is a group of cancers that begin in the bones and soft tissues, which support and connect body structures like muscles, fat, blood vessels, nerves, tendons, and joint linings. Soft tissue sarcoma is the type that starts in the soft tissues. There are many types of sarcomas, and they can occur in various parts of the body. Sarcomas are rare, accounting for about 1% of adult cancers and 15% of childhood cancers. In the U.S., around 16,000 sarcomas are diagnosed annually, including ~4,000 bone sarcomas and ~13,000 soft tissue sarcomas.