Retroperitoneal sarcoma

Learn about this cancer that starts in the soft tissues of the belly, called the retroperitoneum. Treatments include surgery, radiation therapy and medicines.

Update Date: 19.09.2026

Overview
Symptoms
Causes
Risk factors
Diagnosis
Treatment
Alternative medicine
Coping and support
Preparing for an appointment
Stages

Overview

Retroperitoneal sarcoma is a rare cancer that starts in soft tissues in the area behind the organs in the belly. This area, called the retroperitoneum, contains the kidneys, pancreas, parts of the colon and some major blood vessels.

Retroperitoneal sarcoma is a type of soft tissue sarcoma. Soft tissue sarcomas are cancers that begin in tissues that support and connect other parts of the body. Soft tissues include muscle, fat, blood vessels and nerves.

Retroperitoneal sarcomas are rare. They also can be difficult to treat because tumors often grow very large before they cause symptoms. A large tumor may push on or grow into nearby organs, nerves or blood vessels.

The terms "retroperitoneal tumor," "retroperitoneal mass" and "retroperitoneal cancer" do not always mean retroperitoneal sarcoma. A mass in the retroperitoneum can be caused by other cancers or by a noncancerous condition. Tests can help diagnose what type of mass it is.

Retroperitoneal sarcoma can be challenging to treat, but treatment options are available. Surgery is the main treatment when the cancer can be completely removed. Radiation therapy or medicines may be used in some situations, depending on the type, size and location of the cancer and whether it has spread.

Types

There are many types of retroperitoneal sarcoma. The type is based on how the cancer cells look and behave. Each type can behave differently and may require a different approach to diagnosis and treatment.

The most common types include:

  • Liposarcoma. Liposarcoma is a cancer that starts in the fat cells. It can happen anywhere in the body but occurs most often in the belly, arm or leg.
  • Leiomyosarcoma (LMS). This cancer starts in smooth muscle tissue. Many areas of the body have smooth muscle tissue. Leiomyosarcoma most often starts in the uterus, belly or leg. Compared with liposarcoma, leiomyosarcoma is more likely to spread to distant organs.
  • Malignant peripheral nerve sheath tumors (MPNSTs). These tumors start in tissue that surrounds peripheral nerves. These nerves run from the spinal cord into the body. MPNST used to be called neurofibrosarcoma.
  • Solitary fibrous tumor. This tumor starts in the connective tissue and can develop almost anywhere in the body. It often occurs in the lining around the outside of the lungs. It tends to grow slowly.
  • Undifferentiated pleomorphic sarcoma (UPS). The name comes from the way the cancer cells appear under the microscope. Undifferentiated means the cells don't look like 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.

Other types can occur in the retroperitoneum but are not common.

In children, retroperitoneal sarcomas are different from those most often seen in adults. Ewing sarcoma, rhabdomyosarcoma and fibrosarcoma are among the types that can occur in the retroperitoneum in children.

Symptoms

Retroperitoneal sarcoma may not cause any symptoms at first. Because the retroperitoneum is a large space, a tumor can grow quite large before it presses on nearby structures. Many tumors are already large when they are found.

When symptoms occur, they may include:

  • Belly or back pain.
  • A lump or mass in the belly.
  • A feeling of fullness after eating a small amount.
  • Nausea or vomiting.
  • Constipation or bowel blockage.
  • Loss of appetite, trouble eating or unexplained weight loss.
  • Swelling in a leg or both legs or pain that travels into the groin or legs.

Symptoms can depend on the tumor's size and location. For example, pressure on major veins may cause leg swelling. Pressure on nerves can cause pain in the groin or legs. Pressure on the stomach or intestines can cause a feeling of fullness, weight loss or bowel blockage.

High-grade tumors, which tend to grow more quickly, sometimes cause fever, night sweats or flu-like symptoms.

When to seek care

Make an appointment with a doctor or other healthcare professional if you have any ongoing symptoms that worry you.

Causes

It's not clear what causes most retroperitoneal sarcomas.

Soft tissue sarcoma starts when a connective tissue cell gets changes in its DNA. A cell's DNA holds the instructions that tell the cell what to do. In healthy cells, the DNA gives instructions that help control when cells grow, multiply and die.

In cancer cells, the DNA changes give different instructions. These changes tell the cancer cells to grow and divide when they shouldn't or to keep living when healthy cells would die. The cancer cells can build up and might form a mass called a tumor.

The tumor can grow to invade and destroy healthy tissue. In time, cancer cells can break away and spread to other parts of the body. When cancer spreads, it's called metastatic cancer.

Risk factors

Researchers have identified certain factors that can increase the risk of developing some types of sarcoma. But having a risk factor doesn't mean you'll develop the disease.

Factors that can increase the risk of soft tissue sarcoma include:

  • Inherited syndromes. Some syndromes that raise the risk of cancer can pass from parents to children. For instance, syndromes that increase the risk of sarcoma include Li-Fraumeni syndrome, familial retinoblastoma and neurofibromatosis type 1.
  • Radiation therapy for cancer. Radiation treatment for cancer raises the risk of getting a sarcoma later.

Researchers have found characteristic genetic changes within some types of retroperitoneal sarcoma. These changes in the genes can help identify the type of tumor. But these tumor changes usually don't mean that a person inherited the cancer from a parent.

Diagnosis

Diagnosis of retroperitoneal sarcoma usually starts with a review of symptoms and a physical exam. Imaging tests and a biopsy may be used to diagnose this form of cancer.

Physical exam

A healthcare professional may ask when symptoms started and if they've changed over time. A physical exam of the area where symptoms are happening can help the healthcare team understand:

  • The size and depth of the growth.
  • If the growth may be connected to nearby tissues.
  • Whether there are signs of swelling or nerve damage.

Imaging tests

Imaging tests make pictures of the body. They can provide information that helps the healthcare team learn more about your condition. Imaging tests may include:

  • Computerized tomography (CT) scan.
  • Magnetic resonance imaging (MRI).
  • Positron emission tomography (PET) scan.

Retroperitoneal sarcoma may be found when imaging is done because of symptoms or for another reason. If imaging shows a mass in the retroperitoneum, more testing is needed to find out what it is. Not every retroperitoneal mass is a sarcoma.

Biopsy

A biopsy is a procedure to remove a sample of tissue for testing in a lab. The sample may be collected using a needle to draw out some of the tissue. Or sometimes surgery may be needed to remove a tissue sample.

In the lab, doctors trained in analyzing body tissues, called pathologists, look at the tissue sample to examine the types of cells and see whether the cells are likely to be aggressive. This information helps rule out other types of cancer and guide treatment.

Treatment

Treatment for retroperitoneal sarcoma typically involves surgery to remove the cancer when possible. Some people may receive radiation therapy or medicines, such as chemotherapy, targeted therapy or immunotherapy. Treatment depends on factors including the type, size and location of the cancer and whether it has spread.

Surgery

The goal of surgery is to remove the sarcoma completely, along with an area of healthy tissue around it, when possible. Retroperitoneal tumors can grow against or into nearby organs. As a result, the surgeon sometimes needs to remove part or all of a nearby organ along with the tumor. The kidney and colon are among the organs commonly affected.

If a tumor can't be removed completely, your care team may recommend other treatment instead of having surgery right away.

Radiation therapy

Radiation therapy treats cancer with powerful energy beams. The energy beams can come from X-rays, protons or other sources. Radiation therapy might be done before surgery to help control the tumor. Or it might be done after surgery to kill cancer cells that might be left behind. The goal of radiation therapy before or after surgery is to lower the risk of the cancer coming back.

Chemotherapy

Chemotherapy treats cancer with strong medicines. Chemotherapy may be used for some people with retroperitoneal sarcoma, including when the cancer has spread or come back. Sometimes chemotherapy is used before surgery to shrink the cancer so that it's easier to remove. Or chemotherapy may be used after surgery to lower the risk of the sarcoma coming back. The benefit of chemotherapy for localized retroperitoneal sarcoma isn't clear. Localized means the cancer is in one area.

Targeted therapy

Targeted therapy is a cancer treatment that uses medicines to attack specific ways that cancer cells can grow or spread. By blocking these paths, targeted treatments can cause cancer cells to die.

Immunotherapy

Immunotherapy is a cancer treatment with medicine that helps the body's immune system kill cancer cells. Researchers are studying immunotherapy to treat localized and advanced retroperitoneal sarcoma.

Palliative care

Palliative care focuses on relieving symptoms and improving quality of life at any stage of cancer. Treatments such as surgery, radiation therapy or medicines may be used to relieve symptoms even when removing the cancer isn't possible. Palliative care can be provided alongside treatments intended to control the cancer.

Treatment for recurrence

Retroperitoneal sarcoma can come back after treatment. This is called recurrence. The chance of the cancer coming back depends a lot on the type of sarcoma.

Liposarcoma is more likely to come back in the abdomen. Leiomyosarcoma is more likely to spread to other parts of the body. Recurrence can happen even years after surgery, especially with liposarcoma.

If cancer comes back only in the retroperitoneum and can be removed, another surgery may be an option. Treatment depends on where the cancer comes back, how fast it is growing, the type of sarcoma, treatments you've had and your overall health.

If the cancer has spread to other parts of the body, treatment may include medicines that work through the body, such as chemotherapy. Sometimes, surgery, radiation therapy or treatments aimed at specific tumors may be used. When retroperitoneal sarcoma has spread to several areas or other parts of the body, a cure is not common. But treatment may help control the cancer, ease symptoms and help some people live longer. Talk with your care team about the goal of treatment.

The risk of cancer recurrence is often highest during the first 2 to 3 years after surgery. But it also can come back more than five years later. This is why long-term follow-up care is important.

The outlook, called the prognosis, for someone with retroperitoneal sarcoma depends on many things and is different from person to person. Prognosis depends on the features of the cancer and how well treatment works.

Other important factors include whether the cancer has spread to organs or bones and a person's overall health.

Because so many things affect the outlook, cancer statistics such as survival rates can't show exactly how long someone will live.

In general, survival rates for sarcoma are better when the cancer is localized, meaning it has not spread.

Retroperitoneal sarcoma may be cured if it is localized and surgery can remove the entire tumor.

Your care team knows the details of your cancer and treatment. Care team members can give you a personalized outlook and help you make sense of what it means for you. Your care team may share a range of survival to help you plan for the future. Some people want to know as much as possible about prognosis, while others choose to focus on treatment and day-to-day life. It's up to you to decide how much information is helpful.

Alternative medicine

No alternative treatments have been found helpful in treating retroperitoneal sarcoma. But complementary and alternative treatments might help ease some symptoms or side effects of cancer treatment.

Examples of treatments that might help include acupuncture, exercise and massage. Activities called mindfulness-based interventions, such as yoga, relaxation and music therapy, also may be useful. If you're interested in trying alternative treatments, talk with your healthcare professional first.

Coping and support

With time, you may find what helps you cope with worries or other feelings that may come with learning you have retroperitoneal sarcoma. Until then, here are some ideas to help you cope with a cancer diagnosis.

Learn enough about your diagnosis to make decisions about your care

Talk with your healthcare team about retroperitoneal sarcoma. Ask about your test results and treatment choices. As you learn more, you may become more confident in making treatment decisions.

Find a good listener

Finding someone who is willing to listen to you talk about your hopes and fears can be helpful as you manage your diagnosis. This could be a friend or family member. A counselor, medical social worker or clergy member also may offer helpful guidance and care.

Connect with others

Other people who have had sarcoma may be able to offer you support and insight because they understand what you're experiencing. Ask your healthcare team about support groups in your area or contact the American Cancer Society. Find support online through Mayo Clinic Connect, which is a community where you can connect with others for support, practical information and answers to everyday questions.

Preparing for an appointment

Make an appointment with a healthcare professional if you have any symptoms that worry you. If your healthcare professional suspects that you might have retroperitoneal sarcoma, you'll likely be referred to a doctor who treats cancer, called an oncologist.

Retroperitoneal sarcoma is rare, and it often requires complex care. This type of cancer is best handled by a team of experts who have a lot of experience treating it.

Because there's often a great deal of information to talk about, it's a good idea to be prepared for your appointment. Here's some information to help you get ready.

What you can do

When you make the appointment, ask if there's anything you need to do beforehand, such as not eating or drinking for a certain amount of time. Make a list of:

  • Your symptoms, including any pain from where the tumor is located.
  • Key personal information, including medical and surgical history and family medical history.
  • All medicines, vitamins or other supplements you take, including the doses.

Take a family member or friend along, if possible, to help you remember the information you're given.

For retroperitoneal sarcoma, some questions to ask your healthcare professional include:

  • What tests do I need?
  • What are my treatment options?
  • What are the potential side effects of each treatment option?
  • I have other health conditions. How can I best manage them together?
  • Are there brochures or other printed materials I can take with me? What websites do you recommend?

Be sure to ask any other questions you may have.

What to expect from your doctor

Your healthcare professional is likely to ask you several questions, such as:

  • When did your symptoms start?
  • Are your symptoms always present, or do they come and go?
  • How severe are your symptoms?
  • What, if anything, makes your symptoms better?
  • What, if anything, makes your symptoms worse?

Stages

Stage describes how much cancer there is and how far it has spread. Soft tissue sarcomas range from stages 1 through 4. A lower stage generally means the cancer is more limited. A higher stage means it is more advanced or has spread to other parts of the body.

Healthcare professionals determine the stage using several pieces of information, commonly summarized as TNM plus grade. TNM stands for:

  • T: The size of the primary tumor.
  • N: Whether the cancer has spread to nearby lymph nodes.
  • M: Whether the cancer has spread to distant parts of the body.

Grade describes what the cancer cells look like under the microscope. The staging system divides sarcomas into grades 1 to 3. Low-grade tumors tend to be slow-growing and slower to spread and often have a better outlook, called prognosis, than higher grade tumors.

Staging isn't the same for every sarcoma. The tumor's location and type matter, and bone sarcomas have their own staging considerations. So a person's sarcoma can't necessarily be assigned a stage from tumor size alone.

Both tumor grade and stage can help your care team determine the most appropriate treatment.

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