Soft tissues connect, support or surround other tissues. Examples include your muscles, tendons, fat and blood vessels. Soft tissue sarcoma is a cancer of these soft tissues. There are many kinds, based on the type of tissue they started in. Sometimes they spread and can press on nerves and organs, causing problems such as pain or trouble breathing. Embryonal sarcoma is cancer detected in an organism in its early stages of development, especially before it has reached a distinctively recognizable form.