What Is an Undifferentiated Pleomorphic Sarcoma?
An undifferentiated pleomorphic sarcoma is the most commonly diagnosed soft tissue sarcoma that forms in the muscles of adults. Also known as UPS, undifferentiated pleomorphic sarcoma rarely develops as bone sarcoma in the longer bones of the body.
UPS is an undifferentiated sarcoma, meaning its cells haven’t developed into specialized types like normal cells. It’s also a pleomorphic sarcoma, meaning it is made up of cells of various shapes and sizes.
UPS is most often found in the arms, legs, and retroperitoneum, or back half of the abdomen (belly).
UPS tumors can grow quite large and can invade blood vessels and lymph vessels. They can also metastasize (spread), most often to the lungs, and may return even after appropriate treatment.
UPS tumors are rare, with about 1,200 cases found in the U.S. each year. UPS is the most common soft tissue sarcoma, representing 14 percent of cases. Most people affected by these tumors are over 60.
The Sarcoma Program at Penn Medicine’s Abramson Cancer Center is home to one of the nation’s most experienced teams of UPS specialists. We perform sophisticated surgeries that preserve arms and legs and safely navigate in the retroperitoneum. We also offer a range of other leading therapies.
Undifferentiated Pleomorphic Sarcoma Symptoms
Most people with UPS do not notice any symptoms when the tumor is small. Signs that may appear as the tumor grows include:
- Belly discomfort, constipation, loss of appetite, or unintended weight loss when tumors are in the retroperitoneum
- Pain if the tumor pushes on nerves or muscles or affects the joints
- Swelling or lump
What Causes UPS?
Researchers currently don’t know what causes UPS, but they continue to learn more about this cancer.
Research has revealed some factors that may increase your risk of developing UPS:
- Certain bone diseases: A bone condition called Paget disease may increase the chances of developing a sarcoma. Rarely this can include UPS.
- Previous radiation therapy: Undergoing radiation therapy for another disease may increase the risk of eventually developing UPS in soft tissue or bone. However, this side effect of treatment is unusual.
- Family genetics: Some genetic changes can lead to syndromes that raise the risk of UPS. These changes are often inherited from parents, but some develop on their own while in the womb. Two genetic syndromes seem to increase the risk for soft tissue UPS: neurofibromatosis type 1 (NF1) and Li–Fraumeni syndrome (LFS).
Diagnosing UPS Tumors
The most accurate diagnosis of UPS comes from an experienced team that regularly manages this type of sarcoma.
To start, you will have a physical exam; our doctors take time to understand all of your symptoms. Imaging tests give us more information about the tumor, including its size, location, and effect on nearby structures. Magnetic resonance imaging (MRI) is useful for looking at masses in the arms and legs. Computed tomography (CT) is often used for tumors in the retroperitoneum. Scans can also look for signs that the sarcoma has spread.
To confirm a diagnosis, we will perform an image-guided needle biopsy. A pathologist specialized in sarcoma studies this sample under a microscope and performs lab tests on it.
The exam, imaging, and biopsy results help us stage the sarcoma and plan appropriate treatment for you. Learn more about sarcoma diagnosis and staging.
Undifferentiated Pleomorphic Sarcoma Treatment
Treatment for UPS depends on whether the tumor develops in bones or soft tissues.
For soft tissue UPS, we use surgery to remove the tumor safely and completely. Our surgeons excel at the most effective approach to sarcoma surgery—removing the tumor in one piece. They also remove an extra buffer of tissue to reduce the chance that any cancer cells remain.
The surgical approach depends on where UPS is located:
- In the retroperitoneum, operations may require taking out nearby organs in one piece, including the colon, kidneys, spleen, or pancreas.
- In the arms and legs, experienced surgeons use advanced techniques to avoid amputation.
The effectiveness of surgery depends on the tumor’s size, depth, and stage. To reduce the chance that cancer returns in soft tissues, we may recommend adding radiation therapy, usually before the operation. In some cases, we may also recommend chemotherapy.
For bone UPS, our team treats it the same way as a more common bone cancer called osteosarcoma, given shared similarities between their cells.
Chemotherapy may also be used for UPS tumors that are not removable with surgery, for cancer that returns, or cancer that spreads. Immunotherapies, which use the immune system to target cancer, have shown promise in sarcoma clinical trials.
Learn more about sarcoma treatment for UPS at Penn Medicine, including the use of limb-sparing surgery and the development of new therapies.
Make an Appointment
Please call 800-789-7366 or make an appointment.
The Penn Sarcoma Program offers same-day appointments to patients who have their imaging available. To learn more, call 215-349-8200.