Soft Tissue Sarcoma: A Plain-Language Overview

Soft tissue sarcomas are cancers that start in the body's connective and supporting tissues. That includes muscle, fat, blood vessels, nerves, tendons, and the lining of joints. They can form almost anywhere in the body. They most often appear in an arm, a leg, or the belly area. This includes a space deep in the abdomen called the retroperitoneum. There are many subtypes. Each is named for the tissue it most resembles.

A frequent early sign is a painless lump under the skin. It often shows up on an arm or a leg. Harmless lumps are far more common than sarcoma, so most lumps are not cancer. But a lump that sits deep under the skin, is large, or keeps growing is worth having checked. Tumors in the abdomen can grow large before causing symptoms. There is room for them to expand before pressing on anything. Advanced disease can cause pain, breathing trouble, or pressure on nearby organs.

Doctors use imaging to look at the tumor and check for spread. This can include MRI, CT, chest X-ray, and PET scans. A biopsy confirms the diagnosis and the subtype. That means removing a piece of tissue to examine under a microscope. Sarcomas are rare and varied, so this tissue sample should go to a pathologist experienced with sarcoma. Getting the subtype right the first time matters. It shapes every decision that follows.

Several features combine to set the stage. Grade is one. Low-grade tumors tend to grow and spread more slowly. High-grade tumors behave more aggressively. Size matters too. A tumor larger than about 2 inches (5 cm) is treated differently than a smaller one, and again past about 4 inches (10 cm). Spread to nearby lymph nodes matters as well. So does spread to distant sites, such as the lungs. Either kind of spread generally means stage IV disease.

For a small, low-grade tumor, surgery alone is often enough. Surgeons aim for a wide local excision. This removes the tumor with a margin of healthy tissue around it. When the tumor cannot safely be removed this way, radiation can be used instead.

For larger or higher-grade tumors, treatment usually combines more than one approach. Surgery stays central. Radiation is often given before or after the operation, to lower the chance the cancer returns. Chemotherapy may be added for some subtypes, particularly higher-grade or larger tumors.

For sarcoma that has spread, treatment relies more on chemotherapy. Targeted therapy drugs, such as pazopanib or imatinib, help for some subtypes. Imatinib works specifically for a subtype called gastrointestinal stromal tumor, or GIST. This subtype carries a particular gene change that the drug targets. Surgery can still play a role — for example, to remove a tumor that has spread to the lungs. If the cancer comes back, treatment may include another round of surgery, radiation, chemotherapy, or targeted therapy. A clinical trial testing newer immunotherapy drugs may also be worth asking about.

These cancers are rare and very varied. Because of that, treatment at a sarcoma specialist center is linked to getting the diagnosis and treatment plan right. Such a center has surgeons, radiation oncologists, and pathologists experienced in sarcoma. If you or a loved one has a suspected or confirmed sarcoma, it is reasonable to ask about referral to such a center. This is worth doing even for a second opinion before treatment starts.

Ask what subtype of sarcoma you have, and where it is located. Ask whether you can be referred to a specialist sarcoma center, or get a second opinion there. Ask what combination of surgery, radiation, or chemotherapy is recommended, and why. Ask what the goal of treatment is in your specific case. Cure, control, and comfort are different goals, and the goal shapes every choice that follows.

• NCI — Adult Soft Tissue Sarcoma Treatment (PDQ®) Patient Version