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.