Overview

Cancer begins when cells begin to change and grow uncontrollably, forming a mass called a tumor. A tumor can be benign (noncancerous) or malignant (cancerous, meaning it can spread to other parts of the body).

Soft tissue sarcomas (STS) are a group of cancers that develop in the tissues that support and connect the body. STS can occur almost anywhere in the body, and the sarcoma cells resemble the cells that hold the body together, including fat cells, muscle, nerves, tendons, joints, blood vessels, or lymph vessels. When an STS is small, it can go unnoticed or is ignored, since it does not usually cause problems at this stage. As an STS grows, it can interfere with the body's normal activities.

This section covers sarcoma of the soft tissues. For information on a sarcoma that starts in a bone, read the Guide to Bone Cancer. For information on a type of STS called gastrointestinal stromal tumor (GIST) that affects the gastrointestinal tract, read the Guide to GIST.

Sarcomas can appear in any part of the body. About 60% occur in the arms or legs, 30% occur in the trunk or abdomen, and 10% occur in the head or neck. Sarcoma is rare in adults, accounting for about 1% of all adult cancers. However, sarcoma in general, represent about 15% of all cancers in children.

Because there are several different types of STS, it is probably best considered as a family of related diseases, rather than a single, specific disease. The specific types of sarcoma are frequently named according to the normal tissue cells they most closely resemble (Table 1). This is different from how most other types of caner are named by referring to any anatomical site (part of the body) where the disease started.

Table 1: Types of Sarcoma

Grade is the term a pathologist (a doctor who specializes in interpreting laboratory tests and diagnosing disease) uses to describe how aggressive the sarcoma is likely to be, especially in terms of risk of spreading to another site in the body. A low-grade tumor usually has a lower risk of spreading rapidly, and it often stays in the place where it started. A high-grade tumor is more likely to spread to other places, a process known as metastasis.

Experts have identified many types and subtypes of sarcomas. Pathologists are now trying to find new ways to quickly determine a tumor's subtype, as this helps determine treatment. Examination of a tumor's abnormal genetic code may help determine its characteristics and predict which treatments will be most effective. For at least two types of sarcoma, GIST and dermatofibrosarcoma protuberans (DFSP), major advances have been made in a type of treatment called targeted therapy (drug treatments targeted to specific genetic abnormalities in the sarcoma cells).

Find out more about basic cancer terms used in this section.