Sarcoma – Tissue and Systems

This article describes the basic anatomy and systems involved with the cancer sarcoma.  Because the systems involved with sarcoma are so broad, this article will spend more time explaining about sarcoma types rather than the tissues of origin which is essentially the entire body.  Sarcoma is a term that refers to a wide range of cancers that are derived from the fetal tissue types of mesoderm or ectoderm.  This is in contrast to the term carcinoma that refers to cancers from the endodermal germ layer.  Understanding the naming system and complex tumor classifications is not as important for the average person as is understanding what symptoms or signs might indicate the presence of a soft tissue sarcoma.

Sarcoma refers to hundreds of different types of cancer because each one is named based upon the cell type or layer from where it arises.  For example, a tumor of the blood vessel (using the common prefix angio-) is called an angiosarcoma.  Muscle cells are often named with the prefix “myo”, thus tumors of the muscle would be called myosarcoma.  A sarcoma of the bone (using the common prefix osteo-) is called osteosarcoma, and so on.  Not all growths or tumors of these tissues are cancer and it is possible to have a non-cancers tumor as well as a sarcoma grow from the same area.  An example of this would be tumors of fat.  The cells of bodily fat contain lipid and are called adipocytes.  A non-cancerous tumor of fat would be called a lipoma (lip – fat, oma – tumor), whereas a cancerous tumor of fat would be called a liposarcoma.

Sarcomas are rare and represent about 1% of adult cancers and 10% of cancers in children.  About 80-85% of all sarcomas arise from soft tissue (i.e. fat, muscle, vessels), with the rest deriving from bone.

While there are many different types of soft tissue sarcomas, some occur more frequently than others.  A partial list of these common sarcomas includes:

  • Clear cell sarcoma
  • Alveolar soft part sarcoma
  • Malignant mesenchymoma
  • Angiosarcoma
  • Epithelioid sarcoma
  • Fibrosarcoma
  • Rhabdomyosarcoma
  • Nerve sheath tumor
  • Malignant fibrous histiocytoma
  • Liposarcoma
  • Leiomyosarcoma
  • Synovial sarcoma

Most sarcoma tumors occur in people for unknown reasons.  There are several genetics conditions and DNA mutations that have been identified with some sarcomas, but these are the exception rather than the rule.  An example of genetic conditions that lead to sarcomas would be a family affected with the Li-Fraumeni Syndrome.  This syndrome develops from a mutation in the 17th chromosome and can cause multiple types of sarcoma tumors.

The symptoms related to a sarcoma will be directly related to the tissue of origin and some type of compression or interference with function in that area.  It is less common for a sarcoma tumor to cause pain.  About 60-75% of people with a sarcoma will not have any pain.  The most common symptom is the appearance of a painless mass or lump.  The most important point to emphasize of these articles about symptoms of sarcoma is that the appearance of a painless lump that does not go away should be brought to the attention of your doctor. 

Sarcomas tend to grow and spread in a different way compared with most other cancers.  A cancer such as breast or colon cancer will generally disrupt and ulcerate surrounding tissue and find its way to lymph nodes nearby if given enough time.  Sarcomas grow by displacing or pushing the surrounding tissues away.  This pushing of adjacent structures forms what is termed a pseudo-capsule.  When adjacent structures are compressed this can cause symptoms from the tumor.  An example of this would be a tumor of thigh that pushes on veins nearby causing swelling of the leg or involvement of nerves causing weakness or numbness of the leg.

Another unique feature of sarcomas is that they are also classified based on how quickly and abnormally they grow.  These two features are collectively known as tumor grade.  Sarcomas do not have the same tendency to spread to lymph nodes as most other cancers do.  When they do spread, it is usually into adjacent areas and also to the lungs.

The unique growth characteristics of sarcomas make understanding their cell type, size and location even more important.  To understand the precise type of sarcoma requires a sample of the cells involved as well as some type of imaging study.  The best way to image a sarcoma is with a magnetic resonance imaging (MRI) test.  MRI has excellent soft tissue clarity and is much better than a simple x-ray or even CAT scan to view a sarcoma.  To obtain a sample of cells requires a biopsy of some sort.  The most common way this is done is with a needle or small incision to sample it.  It is a very bad idea to simply remove the lump or shell it out.  The reason for this is that this “treatment” will often leave cancer cells behind.

In summary, the key points to understand about sarcoma are: 1) they most commonly appear as painless lumps, 2) they can arise anywhere in the body, 3) it should be brought to the attention of your doctor for further investigation.  Fortunately, most lumps are not sarcoma as this is a relatively rare cancer.  That being said, many cancers do cause some type of swelling or tumor and should not be ignored.

REFERENCES:

  1. www.cancer.gov/cancertopics/types/soft-tissue-sarcoma
  2. www.nlm.nih.gov/medlineplus/softtissuesarcoma.html
  3. Zagars GK, Ballo MT, Pisters PW, et al. Prognostic factors for patients with localized soft-tissue sarcoma treated with conservation surgery and radiation therapy: an analysis of 1225 patients. Cancer 2003; 97:2530.
  4. Abeloff, M.D. (2008). Abeloff: Abeloff’sClinical  Oncology, 4th ed. Chapters 97.Philadelphia,PA: Churchill Livingstone – Elsevier
  5. This article was originally published on September 3, 2012 and last revision and update was 9/4/2015.