Overview

Undifferentiated pleomorphic sarcoma (UPS), formerly referred to as malignant fibrous histiocytoma, is a type of soft tissue cancer. The word "undifferentiated" in undifferentiated pleomorphic sarcoma means that the cells don't resemble the body tissues in which they develop. The cancer is called pleomorphic (plee-o-MOR-fik) because the cells grow in multiple shapes and sizes.

While sarcomas are not common tumors, they do represent one of the most common soft tissue malignancies in adults. Soft tissue sarcomas can develop in blood vessels and in deep skin, fat, muscle, fibrous or nerve tissues.

In particular, UPS usually occurs in the arms or legs, and somewhat less often in the area behind the abdominal cavity (retroperitoneum). The cancer typically becomes quite large over a period of weeks or months, sometimes growing quite rapidly. In most cases, only a rapidly growing UPS causes noticeable pain. Although it tends to grow locally, the cancer can spread to other locations in the body, most often the lungs.

Undifferentiated pleomorphic sarcoma is called a diagnosis of exclusion, meaning it's agreed upon when other diagnoses have been ruled out; it represents less than 5 percent of adult sarcomas.

Symptoms

  • The most common sign of undifferentiated pleomorphic sarcoma is an enlarging, (usually) painless mass, which can become quite large, especially if it develops in a thigh or the retroperitoneum.
  • Sarcomas in the retroperitoneum can also cause pain, lack of appetite, constipation, or bowel or stomach bleeding. The mass can grow big enough to be felt in the abdomen.
  • In cases of extremely rapid growth, you may also feel pain or a sense of compression around the growth, or you may have unexplained tingling, pricking or burning sensations on your skin, or fluid buildup in an affected foot or other extremity.
  • More rarely, you may develop systemic signs and symptoms such as fever or weight loss.

When to see a doctor

Make an appointment with a doctor if you develop any signs or symptoms that seem unusual or that worry you:

  • A new lump or a lump growing on your body
  • Abdominal pain that is getting worse
  • Vomiting
  • Bloody stools
  • Black, tarry stools (when bleeding happens in the stomach or bowels, the blood can turn black as it is digested, and may make stools very black and sticky)

Most often these signs and symptoms come from some other issue than sarcoma, but consult with your doctor regardless.

Causes

Although the causes of UPS are largely unknown, a small percentage (less than 2 to 3 percent) develops at the site of previous radiation therapy. In very rare cases, the sarcoma can also develop in or around chronic ulcers or tissue scarring. A specific cause isn't often identified for most UPS.

Risk factors

Most undifferentiated pleomorphic sarcomas develop in people with no known risk factors. However, some factors may increase their likelihood, including radiation, a damaged lymph system and exposure to certain chemicals.

Again, most people who develop undifferentiated pleomorphic sarcoma have no known risk factors, and many people who have risk factors never develop the cancer.

Undifferentiated pleomorphic sarcoma care at Mayo Clinic

Aug. 08, 2018
References
  1. Ryan CW, et al. Clinical presentation, histopathology, diagnostic evaluation, and staging of soft tissue sarcoma. https://www.uptodate.com/contents/search. Accessed Aug. 21, 2017.
  2. George S, et al. Systemic treatment of metastatic soft tissue sarcoma. https://www.uptodate.com/contents/search. Accessed Aug. 21, 2017.
  3. Mullen JT, et al. Clinical features, evaluation, and treatment of retroperitoneal soft tissue sarcoma. https://www.uptodate.com/contents/search. Accessed Aug. 21, 2017.
  4. Attia S (expert opinion). Mayo Clinic, Rochester, Minn. Sept. 12, 2017.
  5. DeLaney TF, et al. Overview of multimodality treatment for primary soft tissue sarcoma of the extremities and chest wall. https://www.uptodate.com/contents/search. Accessed Aug. 21, 2017.
  6. About soft tissue sarcoma. American Cancer Society. https://www.cancer.org. Accessed Aug. 31, 2017.
  7. Fletcher CDM, et al., eds. World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of Soft Tissue and Bone. Lyon, France: IARC Press; 2002. http://www.iarc.fr/en/publications/pdfs-online/pat-gen/bb5/index.php. Accessed Aug. 31, 2017.
  8. Early detection, diagnosis, and staging. American Cancer Society. https://www.cancer.org. Accessed Aug. 31, 2017.
  9. Causes, risk factors, and prevention. American Cancer Society. https://www.cancer.org. Accessed Sept. 1, 2017.
  10. Treating soft tissue sarcoma. American Cancer Society. https://www.cancer.org. Accessed Sept. 1, 2017.
  11. Garner HW, et al. Preoperative radioactive seed localization of nonpalpable soft tissue masses: an established localization technique with a new application. Skeletal Radiology. 2017;46:209.
  12. Tap W, et al. Randomized phase 3, multicenter, open-label study comparing evofosfamide (Evo) in combination with doxorubicin (D) vs. D alone in patients (pts) with advanced soft tissue sarcoma (STS): Study TH-CR-406/SARC021. Annals of Oncology. 2016;27(suppl 6):13950.
  13. Attia S, et al. A phase Ib dose-escalation study of TRC105 (anti-endoglin antibody) in combination with pazopanib in patients with advanced soft tissue sarcoma (STS). Journal of Clinical Oncology. 2015;33(suppl 15):10514.
  14. Burgess MA, et al. SARC 028: A phase II study of the anti-PD1 antibody pembrolizumab (P) in patients (Pts) with advanced sarcomas. Journal of Clinical Oncology. 2015;33(suppl 15):10578.
  15. Riggin EA. Allscripts EPSi. Mayo Clinic, Rochester, Minn. June 6, 2017.
  16. Goldblum JR, et al. Clinical evaluation and treatment of soft tissue tumors. In: Enzinger and Weiss's Soft Tissue Tumors. 6th ed. Philadelphia, Pa.: Saunders Elsevier; 2014. https://www.clinicalkey.com. Accessed Sept. 1, 2017.
  17. Dangoor A. et al. UK guidelines for the management of soft tissue sarcomas. Clinical Sarcoma Research. 2016;6:20.
  18. Soft tissue sarcoma. Fort Washington, Pa.: National Comprehensive Cancer Network. http://www.nccn.org/professionals/physician_gls/f_guidelines.asp. Accessed March Sept. 7, 2017.
  19. Derbel O, et al. Survival impact of centralization and clinical guidelines for soft tissue sarcoma (A prospective and exhaustive population based cohort). PLOS One. 2017;12:e0158406.http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0158406. Accessed Sept. 7, 2017.
  20. Townsend CM Jr, et al. Soft tissue sarcoma. In: Sabiston Textbook of Surgery: The Biological Basis of Modern Surgical Practice. 20th ed. Philadelphia, Pa.: Elsevier; 2017. https://www.clinicalkey.com. Accessed Sept. 8, 2017.
  21. Goldman L, et al., eds. Malignant tumors of bone, sarcomas, and other soft tissue neoplasms. In: Goldman-Cecil Medicine. 25th ed. Philadelphia, Pa.: Saunders Elsevier; 2016. https://www.clinicalkey.com. Accessed Sept. 8, 2017.
  22. Adult soft tissue sarcoma treatment (PDQ) — Health professional version. National Cancer Institute. https://www.cancer.gov/types/soft-tissue-sarcoma/hp/adult-soft-tissue-treatment-pdq. Accessed Sept. 8, 2017.
  23. Taking time: Support for people with cancer. National Cancer Institute. http://cancer.gov/cancertopics/takingtime. Accessed Sept. 8, 2017.
  24. Niederhuber JE, et al., eds. Sarcomas of soft tissue. In: Abeloff's Clinical Oncology. 5th ed. Philadelphia, Pa.: Churchill Livingstone Elsevier; 2014. https://www.clinicalkey.com. Accessed Sept. 15, 2017.