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.
Symptoms linked to UPS
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
Risk factors for 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).
Finding and evaluating UPS tumors
The most accurate diagnosis of UPS comes from an experienced team that regularly manages this type of sarcoma.
To start, you’ll have a physical exam and a discussion about your symptoms and medical history. Imaging tests help us learn more about the tumor, including its size, location, and whether it has spread to other parts of the body.
To confirm a diagnosis, we may perform an image-guided needle biopsy. A pathologist with expertise in sarcoma examines the tissue sample under a microscope and performs specialized laboratory testing.
The physical exam, imaging, and biopsy results help us determine the stage of the sarcoma and plan appropriate treatment for you.
Advanced treatment for UPS
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.
To reduce the chance that cancer returns in soft tissues, we may recommend radiation before surgery. Additional therapies may also be used depending on the tumor's size, location, and stage.
For bone UPS, our team treats it the same way as a more common bone cancer called osteosarcoma, given shared similarities between their cells.
Additional treatments may be recommended for UPS tumors that can’t be removed 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.
Trusted expertise for complex UPS care
When you’re facing a rare cancer like undifferentiated pleomorphic sarcoma, experience matters. Penn Medicine brings together specialists from across multiple fields who focus on diagnosing and treating sarcomas. By working closely together, our team can evaluate complex cases and recommend the most effective treatment approach for your needs.
Our involvement with the Sarcoma Alliance for Research through Collaboration (SARC) reflects our commitment to improving sarcoma care. Through clinical trials and ongoing research, we’re helping expand treatment options for people with UPS and other rare sarcomas.
Rated “exceptional” by The National Cancer Institute
Penn Medicine’s Abramson Cancer Center is a world leader in cancer research, patient care, and education. Our status as a national leader in cancer care is reflected in our continuous designation as a Comprehensive Cancer Center by the National Cancer Institute (NCI) since 1973, one of 7 such centers in the United States. The ACC is also a member of the National Comprehensive Cancer Network, one of a select few cancer centers in the U.S., that are working to promote equitable access to high-quality, advanced cancer care.