Epithelioid sarcoma

An epithelioid sarcoma is a type of soft tissue sarcoma that typically develops in the forearms and hands. Other locations for these cancerous tumors include the legs and feet, chest, abdomen (belly), pelvis, and back.

Epithelioid sarcomas are the most common soft tissue sarcoma found in the hands and arms. But they’re still very rare—doctors diagnose just 150 epithelioid sarcomas in the U.S. each year; these tumors represent less than 1 percent of soft tissue sarcomas. Most people with the disease are in their 20s, 30s, or 40s. Researchers have not yet discovered what causes epithelioid sarcoma, in large part because it’s so rare.

Despite their slow growth and small size—often less than 3 centimeters across—epithelioid sarcomas are aggressive. They start as a firm growth deep within tissues or along tendons. These cancerous tumors can then spread (metastasize) to nearby structures, including blood vessels and the immune system’s lymph vessels and lymph nodes. They can also spread to the lungs.

The Sarcoma Program at Penn Medicine’s Abramson Cancer Center is home to nationally recognized experts in treating epithelioid sarcoma. Our surgeons are among the nation’s most experienced when it comes to soft tissue sarcomas. Their expertise often allows our team to save affected arms and legs.

Doctors divide epithelioid sarcoma into two types, which differ in who they affect, where they form, and how they are treated. The types include:

• Distal epithelioid sarcoma: This form is more common and mostly affects younger adults. It’s usually found as a small soft tissue mass in the hands, forearms, feet, and legs and tends to spread to nearby lymph nodes.
• Proximal epithelioid sarcoma: This more unusual type of tumor tends to be diagnosed in people with an average age of 40. Proximal epithelioid sarcomas typically form in the back, chest, abdomen, and pelvis. They may act more aggressively and grow to 20 centimeters or more across, making them more difficult to treat.

Since epithelioid sarcomas typically grow slowly without causing pain, most people don't become aware of them right away. However, as the tumor gets larger, you may experience:

• One or more lumps that can continue to grow
• Open skin wound above the lump
• Pain if the tumor forms near a joint or pushes on muscles or nerves
• Swelling

Accurate epithelioid sarcoma diagnosis can be challenging and depends on a thorough evaluation from an experienced team like ours. Because they grow so slowly, these tumors don’t necessarily act like typical cancers. In addition, epithelioid sarcoma tumors feature a mix of cell types. They may appear to be benign (noncancerous) tumors or other cancers when biopsied if not evaluated by an experienced specialist.

At Penn, diagnosis starts by discussing any symptoms and examining any lumps. One of our doctors will also check your lymph nodes and lungs.

Imaging tests can provide some information about the tumor, but a definitive diagnosis of epithelioid sarcoma requires an image-guided needle biopsy. During this procedure, one of our radiologists removes a sample of the tumor, for study under a microscope and lab tests. If you are diagnosed with an epithelioid sarcoma of the arms or legs, we may also recommend taking a biopsy of the sentinel lymph node—the first lymph node likely to be affected if the cancer has spread.

Epithelioid sarcoma treatment at Penn focuses on removing the tumor and any surrounding cancerous cells. Our team has particular expertise in sarcoma surgery that removes the tumor in one piece. Overall treatment effectiveness depends on:

• Age and overall health
• Tumor size, type, and location
• Progress of the disease—if it has invaded blood vessels or lymph nodes or spread farther, for example
• Ability to completely remove cancer around the tumor—doing so reduces the chances the disease will return

Given the possibility that cancer could still come back, we may recommend radiation therapy for epithelioid sarcoma, especially for larger tumors. This treatment is usually done before surgery.

If cancer does return or has already spread, your care team may recommend chemotherapy. The choice of drugs often depends on the type of epithelioid sarcoma diagnosed.

We also recognize the need for newer options to treat advanced epithelioid sarcoma as it is often not responsive to standard sarcoma drugs. One promising development is the approval of a drug called tazemetostat. This drug is part of an innovative approach called epigenetic therapy, which changes how the cancer cells work. In trials, tazemetostat shrank some tumors and controlled the growth of others.

Researchers are also exploring the use of immunotherapy, which harnesses the immune system.

Learn more about sarcoma treatment at Penn Medicine, including the use of limb-sparing surgery, sarcoma clinical trials, and the development of new sarcoma drugs.