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Disease Profile

Undifferentiated pleomorphic sarcoma

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

1-9 / 100 000

US Estimated

Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Malignant fibrohistiocytic tumors; UPS; Malignant fibrous histiocytoma


Musculoskeletal Diseases; Rare Cancers


The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.

Orpha Number: 2023

An aggressive sarcoma of soft tissues or bone that can arise from any part of the body, clinically presenting as swelling, mass, pain, pathological fracture and occasional systemic features and is characterized by high local recurrence and significant metastasis.

UPS ranks the 4th most common soft tissue sarcoma with a slight male preponderance. The incidence has been evaluated to be close to 0.8-1 new case per 100000 per year in one European series.

Clinical description
The tumor arises most commonly during the sixth and seventh decades of life. The most common sites of involvement include lower extremities (mainly thigh) followed by upper arms, retroperitoneum, viscera, head and neck (in childhood). Primary osseous UPS most commonly occurs in distal femur, proximal tibia, proximal femur and humerus. Patients may present pain, swelling / mass and pathological fractures. In the skin, UPS presents as a relatively painless, rapidly enlarging nodule. Anorexia, malaise, fever and weight loss are present in retroperitoneal and inflammatory forms of UPS. Most UPS recur locally; distant metastases are common (the most frequent is lung). Regional metastases are rare.

UPS is thought to be derived from a primitive mesenchymal cell capable of differentiating into histiocytes, fibroblasts, myofibroblasts and osteoclasts. The etiology of the tumor remains unknown. Prior radiation therapy is a likely risk factor in some cases.

Diagnostic methods
Any tumor mass over 5 cm is suspected to be a sarcoma. Magnetic resonance imaging (MRI) is the imaging method of choice for limbs and shows a high signal on T2 weighted images. Histology of biopsy specimen prior to any treatment is crucial to reach diagnosis and shows pleomorphic spindle cell population with large atypical cells frequently exhibiting numerous irregular mitotic figures, associated regions of hemorrhage and necrosis, associated lymphohistiocytic infiltrate and invasion of dermis. Immunohistochemical staining is negative for S-100, HMB-45, CD34 and cytokeratin which assists in ruling out other soft tissue tumors. Most cases previously diagnosed as malignant fibrous histiocytoma have been reclassified into other histological types of sarcoma.

Differential diagnosis
When occurring in skin, UPS is difficult to differentiate from atypical fibroxanthoma or dermatofibrosarcoma protuberans (see this term). Histological differential diagnoses include leiomyosarcoma, rhabdomyosarcoma, lymphoma, and melanoma (see these terms).

Management and treatment
UPS should be referred to an expert/ reference center for primary biopsy, expert pathology review, and multidisciplinary treatment. Immediate surgery of a mass without knowledge of its histological nature is strongly discouraged because it is associated with an increased risk of death due to inappropriate resection and increased risk of relapse. UPS is best treated by wide surgical excision. Sometimes amputation may be necessary to remove the whole lesion. Adjuvant radiotherapy is given for high-grade, large (>5 cm), deep-seated tumors, in limb sparing surgeries and when negative margins are not obtained. For non-operable sarcomas, primary radiation therapy could be an option, but usually doxorubicin containing regimens are preferred options in first-line setting for locally irresectable and/or metastatic lesions. Chemotherapy (CHT) with ifosfamide, trabectedin, dacarbazine, pazopanib have demonstrated efficacy in UPS and are registered and available in most European Union countries.

A 5-year overall survival rate of 48% has been reported for patients with head and neck tumors versus 77% for patients with tumors arising on the trunk and extremities. The childhood variant appears have better prognosis.

Visit the Orphanet disease page for more resources.


This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
80%-99% of people have these symptoms
Abnormality of the lower limb
Lower limb deformities
Abnormality of the peritoneum
Soft tissue sarcoma
30%-79% of people have these symptoms
Abnormality of the musculature
Muscular abnormality
5%-29% of people have these symptoms
Abnormality of the upper limb

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Weight loss


Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

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    These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

    Where to Start

    • The National Cancer Institute provides the most current information on cancer for patients, health professionals, and the general public.

      In-Depth Information

      • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
      • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
      • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
      • PubMed is a searchable database of medical literature and lists journal articles that discuss Undifferentiated pleomorphic sarcoma. Click on the link to view a sample search on this topic.