Cancer starts when cells start to grow out of control. Cells in nearly any part of the body can become cancer and can spread to other areas.

There are many types of soft tissue tumors, and not all of them are cancerous. Many benign tumors are found in soft tissues. The word benign means they’re not cancer. These tumors can’t spread to other parts of the body. Some soft tissue tumors behave in ways between a cancer and a non-cancer. These are called intermediate soft tissue tumors.

When the word sarcoma is part of the name of a disease, it means the tumor is malignant (cancer). A sarcoma is a type of cancer that starts in tissues like bone or muscle. Bone and soft tissue sarcomas are the main types of sarcoma. Soft tissue sarcomas can develop in soft tissues like fat, muscle, nerves, fibrous tissues, blood vessels, or deep skin tissues. They can be found in any part of the body. Most of them start in the arms or legs. They can also be found in the trunk, head and neck area, internal organs, and the area in back of the abdominal (belly) cavity (known as the retroperitoneum). Sarcomas are not common tumors.