Soft tissue sarcoma (adult)


“Soft tissue” is a general term to describe the muscles, tendons, ligaments, tissue around joints, fat, vessels and nerves that make up the body – all these are connective tissues. Cancerous tumors can form in any of these connective tissues. Therefore soft tissue sarcomas can develop anywhere in the body but the most common sites are the arms, legs, trunk, head and neck.  There are many types of soft tissue sarcomas; all are named according to the type of cell that they start in (or that is most visible when biopsied tissue is analyzed).

For example, those that are most prevalent in the extremities (arms or legs) include: 

  Liposarcoma – from fat cells
  Fibrosarcoma – from cells that produce fibrous tissue.
  Leiomyosarcoma – smooth muscle tumors (for example the smooth muscle found in blood vessels)
  Rhabdomyosarcoma – skeletal muscle tumors (muscles that we can control – like our biceps)
  Angiosarcoma – vascular(blood vessel) tumors
  Peripheral nerve sheath tumor – tumors of the nerve cells  
  Ewing sarcoma of soft tissue - (also called extra-skeletal Ewing sarcoma)
  Synovial sarcoma – tumors in the tissue that surrounds the joint

Soft tissue sarcomas are rare tumors. For all types of soft tissue sarcoma, the number of new cases per year in the U.S. is ~12,000.1  

Causes of Soft Tissue Sarcoma

While there is no known cause of a soft tissue tumor, there are inherited disorders that may place a person at risk for developing a sarcoma. These include:

  • Retinoblastoma
  • Neurofibromatosis (von Recklinghausen disease)
  • Bourneville disease
  • Familial adenomatous polyposis (FAP)
  • Li-Fraumeni syndrome
  • Werner syndrome
  • Nevoid basal cell carcinoma syndrome (Gorlin syndrome)

In addition, past radiation therapy for cancer may be a risk factor.

Signs and Symptoms of Soft Tissue Sarcoma

For soft tissue sarcoma of the extremity, the most common sign is a lump that can’t be related to some type of injury. They can be painless or may cause severe pain if they are pressing on other structures such as nerves.

Diagnosing a Soft Tissue Sarcoma

A biopsy is necessary for the diagnosis of a soft tissue sarcoma. The type of biopsy depends on where the tumor is located and an adequate amount of tissue is necessary to accurately diagnose the type of tumor. It is important that the biopsy be done by a specialist with experience in treating extremity sarcomas. A biopsy done incorrectly can affect treatment options for the tumor.

It is important that the biopsy be done by a specialist with experience in treating extremity sarcomas. A biopsy done incorrectly can affect treatment options for the tumor.

Other testing is necessary to determine the size of the tumor and if it has spread to other areas of the body. Testing can include:

      X-ray    An X-ray will see if there is any invasion of the tumor into the bone.
  MRI An MRI will show the size of the tumor and if it is pressing on other structures; it is necessary for surgical planning. It may be used to show if the tumor has spread to the brain.
  PET/CT scan A PET/CT scan is used for staging, to see if the tumor has spread to other areas like the abdomen or lungs.

Grading and Staging of Soft Tissue Sarcoma

The grade of a tumor is a sign of how likely it is to spread (metastasize). The grade of a soft tissue sarcoma is based on three characteristics:

  1. How similar all biopsied tissue looks under a microscope – called differentiation.
  2. How fast the cells are dividing (indicates how fast the tumor is growing) – called mitotic count.
  3. How much of the tumor is made up of dying cells – called tumor necrosis.

A grade of 1 through 3 is then assigned based on these three factors. A higher grade means the tumor is more likely to spread.

The stage of a tumor involves assessment of tumor size, if it has spread to the lymph nodes or other organs, as well as the tumor’s grade. The stages of soft tissue sarcoma are:

  Stage IA – smaller than 5cm (~ 2 inches) across, has not spread and is a grade 1 or the grade can’t be determined.
  Stage IB – larger than 5 cm across, has not spread, and is a grade 1.
  Stage IIA – smaller than 5 cm across, has not spread, and is a grade 2 or 3.
  Stage IIB – larger than 5 cm across, has not spread; and is a grade 2.
  Stage III – larger than 5 cm across, has not spread, and is a grade 3; or, the tumor is of any size and grade and has spread to the lymph nodes.
  Stage IV – the tumor is any size and grade, it has spread to the lymph nodes and/or to other sites like the lungs or brain.

Treatment of Soft Tissue Sarcoma

Surgical removal (resection) is the main treatment for soft tissue sarcoma and for some types of soft tissue sarcoma it is the only treatment needed. It is important that the entire tumor is removed along with a ‘layer’ of normal tissue (called the margin).

Reconstructive surgery may be considered after removal of a soft tissue sarcoma in order to restore appearance and to help with function.

Radiation therapy is often used in addition to surgery to help minimize the chance that the tumor will regrow in the area it was first found (referred to as local recurrence). The decision to have a patient undergo post-operative radiation is typically based on stage of the cancer.

If removal of the entire tumor along with an adequate margin can’t be accomplished because it would affect function, radiation therapy is almost always considered due to the fact that there is some remaining tumor.

Chemotherapy has shown limited benefit for treatment of soft tissue sarcomas. When a tumor cannot be adequately removed due to the location, a course of chemotherapy (usually in combination with radiation therapy) may be considered. Sometimes this will shrink the tumor to the point that it can be safely removed, although a clean margin may not be possible in this situation.

There are a number of clinical trials to help determine if newer chemotherapy medications might show some benefit in treatment of soft tissue sarcoma. Options for clinical trials should be discussed with the treating oncologist.

Prognosis of Soft Tissue Sarcoma

Prognosis, or chance for recovery, from soft tissue sarcoma is closely related to the stage of the disease as well as the patient’s age. In general, individuals over 60 years old have a poorer prognosis than younger patients. Type of soft tissue sarcoma is also a factor with synovial sarcomas having a poor prognosis than liposarcoma, for example.

In general, with all types of extremity sarcoma included, an analysis of data from the National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) database showed the following 5 - year survival information2:

By grade:

  Grade I – 89%
  Grade II – 80%
  Grade III – 57%

If metastatic:

  No – 70%
  Yes – 14%

By tumor size:

  If less than 5 cm across – 75%
  If greater than 5 cm across – 58%
  If unable to determine size – 11%

It is important to keep in mind that every tumor type is different with regard to prognosis so it is best to discuss prognosis related to a specific tumor with the treating physician.


References
1. American Cancer Society: Cancer Facts and Figures 2015. Atlanta, Ga: American Cancer Society, 2015
2. Jacobs AJ, Michels R, Stein J, Levin AS; Improvement in Overall Survival from Extremity Soft Tissue Sarcoma over Twenty Years/ Sarcoma; vol. 2015, Article ID 279601, 9 pages, 2015