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.
Soft tissue sarcoma is a broad term for cancers that start in soft tissues (muscle, tendons, fat, lymph and blood vessels, and nerves). These cancers can develop anywhere in the body but are found mostly in the arms, legs, chest, and abdomen.
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. There are more than 50 different types of soft tissue sarcomas.