Soft tissue sarcoma is a disease in which malignant (cancer) cells form in the soft tissues of the body.

Soft tissues of the body connect, support, and surround other body parts and organs. The soft tissues of the body include the following:

• A mix of bone and cartilage.
• Fibrous tissue.
• Muscles.
• Tendons (bands of fiber that connect muscles to bones).
• Fat.
• Blood vessels.
• Lymph vessels.
• Nerves.
• Tissues around joints (synovial tissue).

Soft tissue sarcomas can form almost anywhere in the body, including the head, neck, and trunk, but are most common in the arms, legs, abdomen, and retroperitoneum.

There are many types of soft tissue sarcoma. The cells of each type of sarcoma look different under a microscope, based on the type of soft tissue in which the cancer began.

For more information about soft tissue sarcomas, see the following:

• Childhood Soft Tissue Sarcoma Treatment
• Gastrointestinal Stromal Tumors Treatment
• Kaposi Sarcoma Treatment
• Uterine Sarcoma Treatment

Having certain inherited disorders can increase the risk of soft tissue sarcoma.

Anything that increases a person's chance of getting a disease is called a risk factor. Not every person with one or more of these risk factors will develop soft tissue sarcoma, and it will develop in people who don't have any known risk factors. Talk with your doctor if you think you may be at risk. Risk factors for soft tissue sarcoma include the following inherited disorders:

• Li-Fraumeni syndrome (TP53 mutation).
• von Recklinghausen disease (neurofibromatosis type 1; NF1 mutation).
• Gardner syndrome (APC mutation).
• Nevoid basal cell carcinoma syndrome (Gorlin syndrome; PTCH1 mutation).
• Tuberous sclerosis (Bourneville disease; TSC1 or TSC2 mutation).
• Werner syndrome (adult progeria; WRN mutation).

Other risk factors for soft tissue sarcoma include the following:

• Past treatment with radiation therapy.
• Having lymphedema in the arms or legs for a long time.
• Being exposed to certain chemicals, such as Thorotrast (thorium dioxide), vinyl chloride, or arsenic.
• Being infected with HIV and human herpesvirus 8. These viruses have been linked to Kaposi sarcoma. For more information, see Kaposi Sarcoma Treatment.

A sign of soft tissue sarcoma is a lump or swelling in soft tissue of the body.

A sarcoma may appear as a painless lump under the skin, often on an arm or a leg. Sarcomas that begin in the abdomen may not cause signs or symptoms until they get very big. As the sarcoma grows and presses on nearby organs, nerves, muscles, or blood vessels, signs and symptoms may include:

• Pain.
• Trouble breathing.

Other conditions may cause the same signs and symptoms. Check with your doctor if you have any of these problems.

Soft tissue sarcoma is diagnosed with a biopsy.

If your doctor thinks you may have a soft tissue sarcoma, a biopsy will be done. The type of biopsy will be based on the size of the tumor and where it is in the body. These types of biopsies may be used:

• Core needle biopsy: The removal of tissue using a wide needle. Multiple tissue samples are taken. This procedure may be guided using ultrasound, CT scan, or MRI.
• Incisional biopsy: The removal of part of a lump or a sample of tissue. An incisional biopsy may be done when a core needle biopsy is not safe to perform or core needle biopsy findings are not clear.

Careful planning of the biopsy should involve the surgeon, a radiation oncologist, and an interventional radiologist who uses medical imaging to guide diagnosis. Samples will be taken from the primary tumor, lymph nodes, and other suspicious areas. A pathologist views the tissue under a microscope to look for cancer cells and to find out the grade of the tumor. The grade of a tumor depends on how abnormal the cancer cells look under a microscope and how quickly the cells are dividing. High-grade tumors usually grow and spread more quickly than low-grade tumors.

Because soft tissue sarcoma can be hard to diagnose, the tissue samples should be checked by a pathologist who has experience in diagnosing soft tissue sarcoma.

The following tests may be done on the tissue that was removed:

• Immunohistochemistry: A laboratory test that uses antibodies to check for certain antigens (markers) in a sample of a patient’s tissue. The antibodies are usually linked to an enzyme or a fluorescent dye. After the antibodies bind to a specific antigen in the tissue sample, the enzyme or dye is activated, and the antigen can then be seen under a microscope. This type of test is used to help diagnose cancer and to help tell one type of cancer from another type of cancer.
• Flow cytometry: A laboratory test that measures the number of cells in a sample, the percentage of live cells in a sample, and certain characteristics of the cells, such as size, shape, and the presence of tumor (or other) markers on the cell surface. The cells from a sample of a patient’s blood, bone marrow, or other tissue are stained with a fluorescent dye, placed in a fluid, and then passed one at a time through a beam of light. The test results are based on how the cells that were stained with the fluorescent dye react to the beam of light.
• Molecular profiling: A laboratory method that uses a sample of tissue, blood, or other body fluid to check for certain genes, proteins, or other molecules that may be a sign of a disease or condition, such as cancer. It can also be used to check for certain changes in a gene or chromosome that may increase a person’s risk of developing cancer or other diseases. It may be done with other procedures, such as biopsies, to help diagnose some types of cancer. It may also be used to help plan treatment, find out how well treatment is working, make a prognosis, or predict whether cancer will come back or spread to other parts of the body.
• Light and electron microscopy: A laboratory test in which cells in a sample of tissue are viewed under regular and high-powered microscopes to look for certain changes in the cells.
• Cytogenetic analysis: A laboratory test in which the chromosomes of cells in a sample of tissue are counted and checked for any changes, such as broken, missing, rearranged, or extra chromosomes. Changes in certain chromosomes may be a sign of cancer. Cytogenetic analysis is used to help diagnose cancer, plan treatment, or find out how well treatment is working.
• FISH (fluorescence in situ hybridization): A laboratory test used to look at and count genes or chromosomes in cells and tissues. Pieces of DNA that contain fluorescent dyes are made in the laboratory and added to a sample of a patient’s cells or tissues. When these dyed pieces of DNA attach to certain genes or areas of chromosomes in the sample, they light up when viewed under a fluorescent microscope. The FISH test is used to help diagnose cancer and help plan treatment.

Certain factors affect treatment options and prognosis (chance of recovery).

The treatment options and prognosis depend on the following:

• The type of soft tissue sarcoma.
• The size, grade, and stage of the tumor.
• Where the tumor is in the body.
• Whether all of the tumor is removed by surgery.
• The patient's age and general health.
• Whether the cancer has recurred (come back).

Small, low-grade tumors, especially in the trunk, arms, or legs, are frequently treated with surgery alone. High-grade sarcomas are more difficult to treat and more likely to spread.