Soft tissue sarcoma

Soft tissue sarcoma is a form of cancer that develops in the connective tissues—blood vessels, cartilage, fat, ligaments, lymph vessels, muscles, nerves, and tendons. These tumors most often occur in the arms and legs (60 percent of cases), but can also be found in the retroperitoneum, or back half of the belly (20 percent of cases), pelvis, spine, neck, head, chest, buttocks, or uterus.

Soft tissue sarcomas are rare, but occur more often than bone sarcomas. They are also more likely to metastasize (spread) before being diagnosed and to return after treatment. Some soft tissue sarcomas are more aggressive than others.

Research shows that people with soft tissue sarcoma often have better outcomes and quality of life when they receive care from a team experienced in treating these rare cancers. The Sarcoma Program at Penn Medicine’s Abramson Cancer Center includes nationally recognized experts who work closely with specialists across many fields, including surgeons who focus on specific areas of the body.

How soft tissue sarcoma may appear

There are more than 50 subtypes of soft tissue sarcomas:

• Alveolar soft part sarcoma, a cancer that usually forms in the legs or buttocks
• Angiosarcoma, a cancer in blood vessels or lymph vessels
• Clear cell sarcoma, a cancer with cells that appear clear and that often starts as small nodules in the feet and hands
• Dermatofibrosarcoma protuberans, a cancer that forms in the layers just beneath the skin, usually on the torso or upper arm or leg
• Epithelioid sarcoma, a slow-growing cancer most often found as a small nodule in the hands or fingers
• Ewing sarcoma, a cancer found more frequently in bones but that can also develop in soft tissues of the arms and legs
• Fibrosarcoma, a cancer of the connective fibrous tissue at the ends of bones of the arms or legs
• Gastrointestinal stromal tumor (GIST), a cancer most often found in the stomach or small intestines
• Kaposi sarcoma, a virus-caused cancer that can show up in the skin or mouth
• Leiomyosarcoma, a cancer found in the smooth muscles of blood vessels and certain organs, most often the uterus
• Liposarcoma, a cancer that begins in fat tissue and forms in the arms and legs and retroperitoneum
• Malignant peripheral nerve sheath tumor, a sarcoma that develops in nerves found beyond the brain and spinal cord—usually in the arms and legs
• Myxofibrosarcoma, a cancer that grows in the muscle but can be closer to the surface of the body in the arms and legs
• Rhabdomyosarcoma (RMS), a cancer that forms in muscles in the head and neck, chest and belly, arms and legs, and pelvis
• Synovial sarcoma, a cancer most often found in the forearms, feet, knees, and thighs
• Undifferentiated pleomorphic sarcoma (UPS), the most common soft tissue sarcoma, which is found in the arms and legs
• Uterine sarcoma, a range of rare cancers found in the uterus

Among the tumors listed, UPS is the most common, followed by liposarcoma, leiomyosarcoma, and GIST.

Doctors know that a particular soft tissue sarcoma called Kaposi sarcoma is caused by a virus called human herpesvirus 8 (HHV8). However, they don’t usually know what causes other soft tissue sarcomas, and you can’t typically reduce your risk of developing one.

Sometimes, radiation therapy can lead to the later development of soft tissue sarcoma, an uncommon side effect that occurs less frequently with newer types of radiation. Another radiation side effect, swelling called lymphedema, can also raise soft tissue sarcoma risk. Past workplace exposure to the chemicals chloride monomer, dioxin, or Agent Orange may also have ties to soft tissue sarcomas.

Some people inherit genetic variants (changes) tied to rare syndromes. These syndromes cause various symptoms and diseases and can raise the risk for some cancers, including sarcomas. The genetic syndromes tied to higher risk for soft tissue tumors include:

• Carney-Stratakis syndrome: GIST
• Familial GIST: GIST
• Familial adenomatous polyposis (FAP): Desmoid tumor (benign)
• Hereditary leiomyomatosis and renal cell cancer (HLRCC): Leiomyosarcoma in the uterus
• Hereditary retinoblastoma: Fibrosarcoma, liposarcoma, leiomyosarcoma
• Li–Fraumeni syndrome (LFS): Rhabdomyosarcoma and, much less frequently, fibrosarcoma, leiomyosarcoma, orbital (near the eyes) liposarcoma, and UPS
• Neurofibromatosis type 1 (NF1): GIST, malignant peripheral nerve sheath tumor, rhabdomyosarcoma, and UPS
• Tuberous sclerosis complex: Various benign soft tissue tumors

A number of additional rare, genetic syndromes can also raise the risk for a type of rhabdomyosarcoma called embryonal rhabdomyosarcoma.

If one of these syndromes runs in your family, specialists at Penn Medicine can provide genetic testing and counseling.

Because soft tissue sarcomas are uncommon, finding experienced specialists is important. At Penn Medicine’s Abramson Cancer Center, we see more than 500 new sarcoma cases and perform more than 100 specialized surgeries each year. Treating a high volume of sarcomas gives our team extensive experience caring for complex and rare tumors.

We offer:

• Specialized expertise: Our dedicated sarcoma team includes surgeons, oncologists, radiologists, pathologists, and others who work closely together to diagnose and treat soft tissue sarcomas.
• Team-based planning: Experts from different specialties review every case together at tumor board meetings to recommend the most effective treatment approach.
• Access to clinical trials: As a member of the Sarcoma Alliance for Research through Collaboration (SARC), we offer access to sarcoma clinical trials and emerging treatments.
• Care across age groups: We partner with the sarcoma program at Children’s Hospital of Philadelphia (CHOP) when appropriate and help younger people transition smoothly to adult care when needed.