The term comes from a Greek word meaning "fleshy growth." Bone tumors (osteosarcomas) are also called sarcomas, but are in a separate category because they have different clinical and microscopic characteristics and are treated differently. Osteogenic sarcoma or osteosarcoma is one of the most common childhood bone cancers. Soft tissue sarcomas are more common in adults than in children. In all, sarcomas constitute less than 1% of all cancers. Its treatment is made more difficult with the existence of more than 70 varieties. Gastrointestinal stromal tumor (GIST) is the most common form of sarcoma, with approximately 3000-3500 cases per year in the United States.