Soft Tissue Sarcoma is a malignant tumour that starts in the cells of the connective and supporting tissues. Malignant means that it can spread, or metastasize, to other parts of the body. It is a rare type of cancer, accounting for about 1% of all adult cancers. However, it is much more common in children, representing about 15% of all childhood cancers. 
Sarcoma can occur in any part of the body, such as the bone or soft tissue. The majority of soft tissue sarcomas occur in a limb, such as an arm or leg. The rest begin in the trunk, abdomen, or head and neck. There are many different types of soft tissue throughout the body, including fat, muscle, tendons, ligaments, blood vessels, and more. Soft tissues exist to support, protect, and connect body tissues and structures.  Sarcomas can also develop in the bone, and behave very differently from soft tissue sarcomas (see Bone Cancer for more information).
Soft tissue sarcoma may go unnoticed at first, as it will be small and not causing any problems. However, as it grows, it can interfere with the body’s normal functions and grow into surrounding tissues and organs. 
Over 1 200 Canadians are diagnosed with soft tissue sarcoma every year. 
 Cancer.net, “Sarcoma, Soft Tissue: Introduction”, https://www.cancer.net/cancer-types/sarcoma-soft-tissue/introduction
 Canadian Cancer Society, “What is soft tissue sarcoma?”, https://www.cancer.ca/en/cancer-information/cancer-type/soft-tissue-sarcoma/soft-tissue-sarcoma/