Soft Tissue Sarcoma

Soft tissue tumors can develop in every type of soft tissue in the body, including nerves, fat, muscle, tendons, the lining of joints, blood vessels, or lymph vessels. They can be malignant (cancerous) or benign. Malignant tumors are known as soft-tissue sarcomas (STS). 

These tumors can occur almost anywhere in the body. About 60 percent of soft tissue sarcomas occur in the legs and arms. They can also occur in the trunk, abdomen, and head and neck region. Tumors that develop in bones and cartilage are discussed under Bone Tumors

When a soft-tissue sarcoma (STS) is small, it can go unnoticed because it usually does not cause problems in the beginning. However, as a STS grows, it can interfere with the body's normal functions.

At UC San Diego Health, people with suspected sarcomas of the abdomen/retorperitoneum and extremities are evaluated by a multidisciplinary team which includes a surgical oncologist, medical oncologist, radiation oncologist, pathologist, and radiologist, all who have expertise in sarcoma, as recommended by current National Comprehensive Cancer Network (NCCN) and European Society of Medical Oncology (ESMO) guidelines. 

You will undergo a thorough evaluation which includes imaging and biopsy (unless biopsy will not change the decision to operate), to obtain an accurate diagnosis and determine the optimal treatment. Soft tissue sarcomas are treated using surgery, radiation therapy or chemotherapy. Depending on the size, location, extent and grade (growth rate) of the tumor, a combination of all or some of these treatments may be used. 

Review the tabs at top of this page for information on soft tissue sarcoma types, diagnosis, and treatment.

Types of soft tissue sarcomas

Because there are at least 60 different types of STS, it is more accurately described as a family of related diseases, rather than a single disease. The specific types of sarcoma are often named according to the normal tissue cells they most closely resemble, as listed below. 

This is different from most other types of cancer, which usually are named for the part of the body where the cancer began. Some sarcomas do not look like any type of normal tissue and are thought to come from stem cells, which are special cells that can mature into specific tissues or organs.

  • Liposarcoma: Develops from fat cells, and occurs most commonly in the legs (at the back of the knee and thigh) and in the abdominal area. The most common form of soft tissue sarcoma, it usually occurs in people between 50 and 70.
  • Leiomyosarcoma: This rare tumor develops from smooth muscle tissue, the tissue that makes up involuntary muscle. This type of muscle is found throughout the body, including in the stomach and intestines, the brains, blood vessel walls, skin, and uterus. Leiomyosarcoma occurs most commonly in the abdomen and extremities, but can also affect blood vessels and internal organs and tends to be very aggressive.
  • Rhabdomyosarcoma: This very rare tumor, which affects fewer than 400 people annually in the U.S., generally develops in muscle tissue. It's most common in children and young adults. In young children, it tends to occur in the head and neck, bladder, and vagina, while in older children and young adults it develops in the large muscles of the extremities and the trunk; in adults, it tends to form in the large muscles of the extremities.
  • Synovial sarcomas: This tumor develops near joints and is named for its molecular resemblance to synovial tissue, the tissue lining of the joints. However, it is not believed to arise from this synovial tissue. About 50 percent of synovial sarcomas occur in the legs, followed by the arms.
  • Gastrointestinal stromal tumors (GIST): These develop in the interstitial cells of Cajal (ICC), which are cells that line the walls of the gastrointestinal tract. These cells signal muscles to contract to move food and liquid along the digestive tract. Most GIST tumors are found in the stomach, but can also occur in the small intestine, esophagus, colon, and rectum. They generally occur in people between 50 and 70. Learn more about GIST.
  • Fibrosarcoma: Develops in the fibrous tissue found at the end of long bones in the arms and legs, and in the trunk. It's most common in adults under 60; although, older adults and infants can also be affected.
  • Undifferentiated pleomorphic sarcoma (previously known as malignant fibrous histiocytoma or MFH): These develop in fibrous tissue in the arms and legs and occur most often in older adults.
  • Angiosarcomas: Develop in the blood or in lymph vessels. They most commonly occur in skin, soft tissue, liver, breast, spleen, bone, lung and heart.
  • Kaposi’s sarcoma: This cancer of the lining of the lymph or blood vessels occurs most often in patients with AIDS.

Often, soft tissue sarcomas present no symptoms in their early stages.

When sarcomas develop on the arms or legs, they can cause a lump that grows over a period of time. It may or may not be painful. A sarcoma can cause pain as it grows and exerts pressure on nerves and muscles.

Other symptoms can include worsening abdominal pain and blood in your stool or vomit.

If your physician suspects a soft tissue sarcoma, he or she will order a biopsy so tissue samples can be examined by a pathologist under a microscope. The type of biopsy will be based on the size and location of the tumor. Biopsy types include:

  • Incisional biopsy: The removal of part of a lump or a sample of tissue
  • Core biopsy: The removal of tissue using a wide needle


The stage of a cancer describes its size and whether it has spread beyond its original area of the body. In sarcoma staging, doctors also evaluate the appearance of the tumor under the microscope and judge how fast the cancer seems to be growing.

  • IA: The cancer cells look either very much like normal cells or somewhat different from normal. The cancer is less than five centimeters (about two inches) in size, and has not spread to lymph nodes or other parts of the body. It may be near the surface or deep.
  • IB: The cancer cells look either very much like or somewhat different from normal cells. The cancer is near the surface and more than five centimeters in size, but it has not spread to lymph nodes or other parts of the body.
  • IIA: The cancer cells look either very much like normal cells or somewhat different from normal. The cancer is deep and more than five centimeters in size, but it has not spread to lymph nodes or other parts of the body.
  • IIB: The cancer cells look very different from normal cells. The cancer is either near the surface or deep and is less than five centimeters in size, but it has not spread to lymph nodes or other parts of the body.
  • IIC: The cancer cells look very different from normal cells, the cancer is near the surface, is more than five centimeters in size, but it has not spread to lymph nodes or other parts of the body.
  • III: The cancer cells look very different from normal cells. The cancer is deep and is more than five centimeters in size, but it has not spread to lymph nodes or other parts of the body.
  • IV: The cancer may have spread to lymph nodes in the area or may have spread to other parts of the body, such as the lungs, head, or neck.
  • Recurrent: The cancer has returned (recurred) after being treated. It may recur in the tissues where it originally started, or elsewhere.

Treatment options for soft tissue sarcomas include surgery, radiation therapy, and chemotherapy.

At UC San Diego Health, our oncology team will determine the best treatment or combination of treatments you, depending on the type and stage of your sarcomas.


The primary treatment for most soft tissue sarcomas is surgery to remove the tumor. Depending on the type and extent of the tumor, surgical options include:

Wide local excision: Surgical removal of the tumor (excision) along with some normal tissue around it.

Organ-sparing surgery: In the past, treatment for primary malignant soft tissue sarcomas of the abdomen/retroperitoneum often included resection of adjacent organs. However, advances in surgical techniques (including minimally invasive procedures), as well as chemotherapy and radiation treatments have resulted in new organ-sparing surgical procedures. The goal of organ-sparing surgery is the complete removal of the tumor with preservation of adjacent organs and function. At UC San Diego Health, the surgical oncology team has experience and expertise in these organ-sparing surgical techniques. In cases where organs/vessels needs to be removed, reconstructive/vascular surgery can be performed to maintain function.

Lymphadenectomy: Surgical removal of the lymph nodes that contain cancer.

Radiation therapy

This treatment with high-dose X-rays can be used before surgery to shrink soft tissue tumors and make them easier to remove. It's sometimes used after surgery to kill any cancer cells that may have been left behind.

We use the advanced technology known as intensity modulated radiation therapy, or IMRT, to precisely target the tumor and reduce damage to surrounding healthy tissues.


Chemotherapy, the use of anti-cancer medications, may be used to shrink tumors and make the tumor more accessible for removal by surgery or radiation treatment. Chemotherapy before surgery is called neoadjuvant treatment.

Chemotherapy that follows radiation or surgery is known as adjuvant treatment, and is used to destroy any remaining malignant cells in order to decrease the risk of recurrence.