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.

  • 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.

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.

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.

Initial evaluation for a suspected undifferentiated pleomorphic sarcoma usually starts with a history of when you first noticed the mass and how quickly it's been growing, as well as a physical examination. Your physical exam should focus on the current size and depth of the mass, whether it's connected to nearby normal tissues, and any signs of associated swelling or nerve damage.

Your doctors will want to check whether your mass is one of several much more common benign conditions, such as soft tissue tumors (for example, lipomas). Other malignant tumors should also be ruled out, including lymphoma, melanoma, carcinoma that has metastasized, or one of several other sarcomas.

Because benign soft tissue tumors are so much more common than undifferentiated pleomorphic sarcoma or other malignant soft tissue sarcomas, it can be challenging to assess which soft tissue masses call for further evaluation. Published criteria for urgent referral of a patient with a soft tissue lesion focus on three aspects:

  • A soft tissue mass, golf ball-sized or larger
  • A painful lump
  • A lump that's increasing in size

Also, deeper lying masses are more likely to be sarcomas, as are lumps that redevelop after being surgically removed. The more of these clinical features exist, the greater the chance of malignancy. Increasing size is the strongest individual indicator.

  • Undifferentiated pleomorphic sarcoma is best treated with a multidisciplinary approach that involves medical oncologists, pathologists, radiologists, surgeons, radiation therapists and others.
  • Early referral to such a multidisciplinary center — one that sees and treats a high number of such cases annually — is associated with better outcomes.
  • Even the initial biopsy should be done at the same treatment center, as well as any resection surgery.

In almost all instances your doctor will likely recommend you undergo diagnostic tests, including:

  • Imaging tests. Imaging tests, such as X-rays, computerized tomography (CT) scans, magnetic resonance imaging (MRI) and positron emission tomography (PET), may be used to evaluate the area of concern. The evaluation itself may include defining the source of a tissue mass, determining the extent of a primary tumor for surgical planning, and tests to indicate whether any malignant growth has metastasized to additional locations such as a lung.
  • Tissue sample removal and testing (biopsy). Your doctor may perform a biopsy procedure to remove a sample of the suspected sarcoma for testing in a lab. To remove the sample, your doctor may use a long, thin needle. Sometimes a biopsy sample is removed during surgery.

Again, if undifferentiated pleomorphic sarcoma is suspected, it's often best to seek care at a medical center that sees many people with this type of cancer. Experienced doctors will select the best biopsy technique to ensure proper surgical treatment and planning.

In the lab, a doctor trained in analyzing body tissues (pathologist) examines the tissue sample for signs of cancer. The pathologist also analyzes the sample to understand the type of cancer and to determine whether the cancer is aggressive.

Treatment options for undifferentiated pleomorphic sarcoma will depend on the size and location of your tumor.


Surgery is typically the primary treatment for UPS. The goal is to remove the cancer and a margin of healthy tissue around it with as minimal an impact as possible. When UPS affects the arms and legs, this means using limb-sparing techniques whenever feasible.

However, in some cases it may be necessary to amputate the affected arm or leg. Doctors work very hard to avoid amputation. For example, they may recommend radiation therapy to shrink the tumor before surgery, which can decrease the chances that an amputation will be needed.

If undifferentiated pleomorphic sarcoma spreads to another area of the body, it may be possible to surgically remove the other tumor, subject to its particular medical needs.

Radiation therapy

Radiation therapy involves treating cancer with high-powered beams of energy, such as X-rays or protons.

  • Your doctor may suggest using radiation therapy before an operation in order to shrink a tumor to make it easier to remove.
  • Radiation may also be used after surgery to kill any cancer cells that remain.
  • Radiation may also be employed during surgery just after a resection, a procedure called intraoperative radiation therapy (IORT).


Chemotherapy is a drug treatment that uses chemicals to kill cancer cells. It can be administered by pill or through a vein (intravenously), or both. While it's generally not used in early-stage UPS, chemotherapy may be used to treat tumors that have spread to other parts of the body or to treat more-advanced disease.

Chemotherapy may also be combined with radiation.

Targeted chemotherapy drugs used to treat undifferentiated pleomorphic sarcoma include:

  • Doxorubicin (Doxil) with olaratumab (Lartruvo)
  • Gemcitabine (Gemzar) with docetaxel (Taxotere)

These medications and others may be prescribed at the discretion of your doctor.

No alternative treatments have been found helpful in treating undifferentiated pleomorphic sarcoma. But some complementary and alternative treatments may relieve the symptoms you experience due to cancer or cancer treatment.

Alternative treatments that may help relieve symptoms include:

  • Acupuncture
  • Aromatherapy
  • Massage
  • Meditation
  • Relaxation exercises

Resources such as the American Cancer Society and the National Cancer Institute offer more information on complementary and alternative treatment options as well as further advice on symptom relief.

A diagnosis of cancer such as undifferentiated pleomorphic sarcoma can be overwhelming. With time you'll find ways to cope with the distress and uncertainty of cancer. Until then, you may find it helps to:

  • Learn enough about UPS to make decisions about your care. Ask your doctor about your sarcoma, including your treatment options and, if you like, your prognosis. As you learn more about UPS, you may become more confident in making treatment decisions.
  • Keep friends and family close. Keeping your close relationships strong will help you deal with your UPS diagnosis and care implications. Friends and family can provide the practical support you'll need, such as helping take care of your house if you're in the hospital. And they can serve as emotional support when you feel overwhelmed by cancer.
  • Find someone to talk with. Find a good listener who is willing to listen to you talk about your hopes and fears. This may be a friend or family member. The concern and understanding of a counselor, medical social worker, clergy member or cancer support group also may be helpful.

    Ask your doctor about support groups in your area. Or check your phone book, library or a cancer organization, such as the National Cancer Institute or the American Cancer Society.

If your family doctor suspects you have undifferentiated pleomorphic sarcoma, you'll likely be referred to a cancer doctor (oncologist) who specializes in sarcomas. Undifferentiated pleomorphic sarcoma is rare and often requires complex care. It's best treated by someone who has significant experience with it, which often means an academic or multispecialized cancer center.

Because appointments can be brief, and there's often a lot of ground to cover, it's a good idea to arrive well-prepared. Here's some information to help you get ready.

What you can do

  • Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
  • Make a list of all medications, vitamins or supplements that you're taking.
  • Ask a family member or friend to come with you. Sometimes it can be difficult to remember all the information provided to you during an appointment. Someone who accompanies you may remember something that you missed or forgot.
  • Write down questions to ask your doctor.

Your time with your doctor is limited, so preparing a list of questions can help you make the most of your time together. List your questions from most important to least important in case time runs out. For undifferentiated pleomorphic sarcoma, some basic questions to ask your doctor include:

  • Do I have cancer?
  • Are there other possible causes for my symptoms?
  • What kinds of tests do I need to confirm the diagnosis? Do these tests require any special preparation?
  • What stage is the sarcoma?
  • What treatments are available for undifferentiated pleomorphic sarcoma, and which do you recommend?
  • Can the sarcoma be removed?
  • What types of side effects can I expect from treatment?
  • Are there any alternatives to the primary approach that you're suggesting?
  • I have other health conditions. How can I best manage these conditions together?
  • Are there any dietary or activity restrictions that I need to follow?
  • What's my prognosis?
  • Are there any brochures or other printed material that I can take with me? What websites do you recommend?
  • Should I get additional treatments such as radiation therapy either before or after an operation?
  • Is the surgeon you're recommending experienced in this specific type of cancer operation?

What to expect from your doctor

Your doctor is likely to ask you a number of questions. Being ready to answer them may make time to cover other points you want to discuss. Your doctor may ask:

  • When did you first notice your signs and symptoms?
  • Are you experiencing pain?
  • Does anything seem to improve your symptoms?
  • What, if anything, appears to worsen your symptoms?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask other questions.

Last Updated: 08-08-2018
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