Sarcoma, Soft Tissue

Cancer begins when normal cells change and grow uncontrollably, forming a mass called a tumor. A tumor can be cancerous or benign. A cancerous tumor is malignant, meaning it can spread to other parts of the body. A benign tumor means the tumor will not spread.

About sarcoma

Sarcoma can start in any part of the body, such as the bone or soft tissue. About 60% of soft tissue sarcomas begin in an arm or leg, 30% start in the torso or abdomen, and 10% occur in the head or neck. Both children and adults can develop a sarcoma, but it is rare in adults, accounting for about 1% of all adult cancers. However, sarcoma in general represents about 15% of all childhood cancers.

This section covers sarcoma of the soft tissues. Learn more about sarcoma that starts in a bone.

About soft-tissue sarcoma

Soft-tissue sarcomas (STS) are a group of cancers that begin in the tissues that support and connect the body, such as fat cells, muscle, nerves, tendons, the lining of joints, blood vessels, or lymph vessels. As a result, STS can occur almost anywhere in the body. When an STS is small, it can go unnoticed because it usually does not cause problems in the beginning. However, as an STS grows, it can interfere with the body's normal functions.

Because there are at least 50 different types of STS, it is more accurately described as  a family of related diseases, rather than a single disease. The specific types of sarcoma are often named according to the normal tissue cells they most closely resemble, as listed below. This is different from most other types of cancer, which usually are named for the part of the body where the cancer began. Some sarcomas do not look like any type of normal tissue and are thought to come from stem cells, which are special cells that can mature into specific tissues or organs.

Name of Sarcoma

Related Normal Tissue Type

Alveolar soft part sarcoma

No obvious related normal tissue; may be a tumor of stem cells


Blood or lymph vessels

Desmoid tumor , also called deep fibromatosis

Fibroblasts, which are  the most common type of cells in connective tissue

Ewing Family of sarcomas, including peripheral primitive neuroectodermal tumors (PNET)

No obvious related normal tissue; may be a tumor of stem cells


Fibroblasts, which are the most common type of cells in connective tissue

Gastrointestinal stromal tumor (GIST)

Specialized neuromuscular cells of the digestive tract

Kaposi sarcoma

Blood vessels


Smooth muscle


Fat tissue


Connective tissue

Malignant peripheral nerve sheath tumor (MPNST), also known as neurofibrosarcoma

Cells that wrap around nerve endings, similar to the way insulation wraps around a wire


Skeletal muscle

Synovial sarcoma

No obvious related normal tissue; may be a tumor of stem cells

Undifferentiated pleomorphic sarcoma (UPS), often referred to as malignant fibrous histiocytoma (MFH) in the past

No obvious related normal tissue; may be a tumor of stem cells or a distant relative of rhabdomyosarcoma

The list above is not a complete list, but several of the most common types are listed. Experts have found many types and subtypes of sarcomas. Pathologists are now trying to find new ways to quickly determine a tumor's subtype because this helps determine treatment. A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease.  Looking at a tumor's abnormal genetics may help determine its characteristics and predict which treatments will be most effective. The use of targeted therapy has resulted in major advances in treating several types of sarcoma, including GIST, dermatofibrosarcoma protuberans (DFSP), tenosynovial giant cell tumor, and desmoid tumors. 

Pathologists also describe sarcoma by the grade, which describes how much cancer cells look like healthy cells when viewed under a microscope. The grade can help the doctor predict how quickly the sarcoma will spread. In general, the lower the tumor’s grade, the better the prognosis, which is the chance of recovery. Learn more about grade in the Stages and Grades section.

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