Types of Tumors

Bone & soft tissue ("musculoskeletal") tumors can be benign, malignant or metastatic. Benign tumors do not spread from their original location and, therefore, do not threaten patient survival. However, they can damage or destroy tissues and may be very painful. Benign tumors with an increased tendency to come back (“recur”) after surgical removal are often described as "aggressive". However, this does not mean they can spread.

Malignant tumors have the capacity to spread to other parts of the body. These are referred to as cancers.  The likelihood of a tumor to spread to other tissues, and thus the risk to the patient, depends on a tumor's "grade" (see below). Often, malignant tumors are treated with surgery combined with radiation and/or chemotherapy. When a cancer arises in bone, muscle or connective tissue, it is called a "sarcoma".

Metastatic tumors are cancers that have spread from one location to another. The most common scenario is a carcinoma, i.e. a cancer that originates in an organ, to spread to the bones. The most common bones affected are the spine, pelvis and hips. The most common sources are breast, kidney, lung, thyroid and prostate cancers. In these cases, treatment is primarily directed by a medical oncologist who will select chemotherapy depending on the type of cancer. Our center will typically be involved when damage to the bones threatens or has already caused a fracture. In some of these cases, surgery can reduce pain and improve quality of life for the patient.


An example of a soft tissue sarcoma grossly distending a muscle but remaining within it

Sarcomas are malignant tumors of the musculoskeletal system. Sarcoma is cancer. Most people of more familiar with cancers which arise from organs, such as breast, lung and colon cancer. These types of cancer are collectively called “carcinoma”. Sarcoma is rare, representing less than 1% of all cancers.

There are many types of sarcomas. In general, bone sarcomas are more common in children and teens and soft tissue sarcomas more common in adults. All sarcomas share some common traits, which differentiate them from carcinomas:

  • sarcoma primarily spreads via the blood stream, not the lymphatic system as with carcinoma, therefore most sarcoma surgery does not include removal of lymph nodes
  • sarcoma tends to push rather than infiltrate adjacent structures, so even very large tumors can usually be surgically removed
  • many sarcomas are "low grade" (see below), some even large ones, and thus pose low risk to the survival of the patient 

Soft Tissue Sarcoma

The words "soft tissue" confuse many people. Soft tissues are what hold the body together. They include muscles, tendons, blood vessels, fat, nerves, and deep skin tissues. Soft tissues do not include bones or other organs. Although body parts such as lungs, breasts, and colons are soft, they have specific functions. Because they perform very specific “jobs,” they are not considered part of the "soft tissues".

Soft tissue sarcoma is cancer in one of the soft tissues. There are many different kinds of soft tissue sarcoma. In general, soft tissue sarcomas are rare. About 43 percent of soft tissue tumors start in the arms or legs. Most of the others are found in the torso, or trunk area. Less often, they are found in the head and neck or inside other organs, including the liver, lung, kidney, uterus, breast, gastrointestinal tract, or the abdominal cavity.

We do not know a lot about what causes soft tissue sarcoma. They do know, however, that injuries do not cause the disease. Because these tumors are rare, if you have soft tissue sarcoma, it is important to seek the care of a musculoskeletal tumor specialist.

Grading and Staging

Lung nodule from sarcoma that has metastasized

Grade is a measure of the aggressiveness of the tumor as seen microscopically by the pathologist. Sarcomas are usually graded as “low”, “intermediate” or “high”. Tumors that are “high” grade are the most likely to spread or to come back.

When sarcomas spread to other parts of the body, by far the most common location  is the lungs. Thus all patients with sarcoma will undergo CT scanning of the lungs on a regular basis. If metastasis to the lungs is discovered, in many cases a portion of the lung containing the tumor can be removed.

The three things that can help predict the future behavior of a sarcoma are:

  1. Tumor grade (low, intermediate or high)
  2. Tumor size (less than or greater than 5 centimeters, i.e. ~2 inches)
  3. Tumor location, specifically whether it is under the skin or deeper under the muscles

Taken together, the above three pieces of information are combined into the sarcoma "stage". Assigning a stage to a sarcoma is an attempt to try to predict its future course. Stages range from I (one) to IV (four). The higher the stage, the more worrisome its behavior. 

Low grade sarcomas are almost always Stage I. Intermediate and high grade sarcomas are either Stage II or III. Stage IV sarcomas are those which have already spread, i.e. metastasized. 

It is very important to remember that tumor staging is designed to help doctors compare treatments and outcomes for large populations of patients. It can only offer a very rough prognosis for an individual patient. It does not predict the future and certainly cannot tell us "how long somebody has to live".