Sclerosing epithelioid fibrosarcoma, or SEF, is a type of rare cancer that grows in the soft tissues and bones throughout the body. It usually grows in the arms, legs, head and neck, but can be found anywhere in the body. Soft tissues include the muscle, fat, tendons, ligaments, lymph and blood vessels, nerves, or other tissue that connects and supports the body.

SEF is a type of cancer called soft tissue sarcoma. SEF gets its name from how the cells that make up this tumor look under the microscope. The cells look like they are arranged in strands and sheets. Sometimes this tumor is confused for a different kind of rare sarcoma called fibromyxoid sarcoma, because these tumors look alike under the microscope. SEF was first described as a unique tumor in 1995.

SEF is so rare that there is little data on how many people have it. SEF seems to be more common in adults but there have been cases of children with SEF. Some studies estimate that 10 to 20% of people with SEF are under 30 years old.

Scientists are always working to understand how cancer forms, but it can be hard to prove. We know that in SEF, chromosomes (the parts of your cells that contain all of your genes) break apart and get put back together in the wrong way. This can cause cells to not function like they should. In some cases of SEF, a gene called FUS joins with a region called CREB3L1 or CRE3BL2. In other cases of SEF, the gene EWSR1 joins with a region called CREB3L1.

SEF does not run in families.

Some people with SEF do not have symptoms when the cancer first starts. Later, when the tumor gets larger, symptoms can depend on where the tumor is growing in the body. Tumors that grow in the arms or legs may cause pain or weakness in the arms or legs. Tumors that grow in the chest may cause shortness of breath and cough. Tumors that grow in the head may cause headache.

Imaging: If you have symptoms of SEF, your doctor will use imaging scans such as X-ray, CT, and MRI to look at where the tumor is and how big it is. They will also check for signs that the tumor has spread to other parts of the body.

Biopsy: To check if the tumor is SEF, your doctor will do a biopsy, taking a small sample from the tumor with a needle. An expert, called a pathologist, will study cells from the sample under the microscope to see what kind of tumor it is. They will also look for certain changes in chromosomes to confirm that your cancer is SEF.

Treatment for each patient will be unique. You should go to an expert in sarcoma treatment to decide the best approach for your tumor. You can contact MyPART for help finding experts near you.

Treatment options to discuss with your doctor include:

Surgery: Surgery may be used to remove the as much of the tumor as possible.

Chemotherapy: In some cases of SEF that have spread to other parts of the body, chemotherapy may be used. But, there are not much data showing that chemotherapy is effective in treating SEF.

Radiation therapy: Radiation therapy can be used around the time of surgery. The radiation is aimed at the tumor area to prevent it from growing back after it is removed.

Immunotherapy: Immunotherapy helps the body’s immune system fight the cancer cells.

The estimate of how a disease will affect you long-term is called prognosis. Every person is different and your prognosis will depend on many factors, such as:

• Where the tumor is in your body
• If the cancer has spread to other parts of your body
• How much of the tumor was taken out during surgery

If you want information on your prognosis, it is important to talk to your doctor. Also, NCI has resources to help you understand cancer prognosis.

Doctors base SEF survival rates on how groups of people with SEF have done in the past. Because there are so few people with SEF, these rates may not be very accurate.

The prognosis of SEF depends on where the tumor is in the body and if it has spread. One study estimates that tumors come back in at least 50% of patients. The cancer spreads to other parts of the body in 43% to 86% of people with SEF.

Because SEF is likely to come back in the same spot or spread to different parts of the body after treatment, it is very important to have regular follow-up visits with your doctor.