Soft tissue sarcoma

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Overview
A soft tissue sarcoma is a malignant (cancerous) tumor that develops in mesenchymal tissue. Mesenchymal tissues encompass all the muscle, connective tissues, and bones of the body.

Soft tissue sarcomas can invade surrounding tissue and can metastasize (spread) to other organs of the body, forming secondary tumors. The cells of secondary tumors are similar to those of the primary (original) cancer. Secondary tumors are referred to as "metastatic soft tissue sarcoma" because they are part of the same cancer and are not a new disease. The most common site of spread is to the lungs.

Some tumors of the soft tissue are benign (noncancerous) and are not sarcomas. These tumors do not spread and are rarely life-threatening. However, benign tumors can crowd nearby organs and cause symptoms or interfere with normal body functions.

Causes
Scientists do not fully understand why some people develop sarcomas while the vast majority do not. The vast majority develop in patients with no known risk factors or identifiable etiology. However, by identifying common characteristics in groups with unusually high occurrence rates, researchers have been able to single out some factors that may play a role in causing soft tissue sarcomas.

Studies suggest that workers who are exposed to Phenoxy herbicide in herbicides and chlorophenols in wood preservatives may have an increased risk of developing soft tissue sarcomas. An unusual percentage of patients with a rare blood vessel tumor, angiosarcoma of the liver, have been exposed to vinyl chloride in their work. This substance is used in the manufacture of certain plastics.

In the early 1900s, when scientists were just discovering the potential uses of radiation to treat disease, little was known about safe dosage levels and precise methods of delivery. At that time, radiation was used to treat a variety of noncancerous medical problems, including enlargement of the tonsils, adenoids, and thymus gland. Later, researchers found that high doses of radiation caused soft tissue sarcomas in some patients. Because of this risk, radiation treatment for cancer is now planned to ensure that the maximum dosage of radiation is delivered to diseased tissue while surrounding healthy tissue is protected as much as possible.

Researchers believe that a retrovirus plays an indirect role in the development of Kaposi's sarcoma, a rare cancer of the cells that line blood vessels in the skin and mucus membranes. Kaposi's sarcoma often occurs in patients with AIDS (acquired immune deficiency syndrome). AIDS-related Kaposi's sarcoma, however, has different characteristics and is treated differently than typical soft tissue sarcomas.

Studies have focused on genetic alterations that may lead to the development of soft tissue sarcomas. Scientists have also found a small number of families in which more than one member in the same generation has developed sarcoma. There have also been reports of a few families in which relatives of children with sarcoma have developed other forms of cancer at an unusually high rate. Sarcomas in these family clusters, which represent a very small fraction of all cases, may be related to a rare inherited genetic alteration of the p53 gene and is known as Li-Fraumeni syndrome.

Certain other inherited diseases are associated with an increased risk of developing soft tissue sarcomas. For example, people with neurofibromatosis type I (also called von Recklinghausen's disease associated with alterations in the NF1 gene) are at an increased risk of developing soft tissue sarcomas known as malignant peripheral nerve sheath tumors. Patients with inherited retinoblastoma have alterations in the RB1 gene, a tumor suppressor gene, and are likely to develop soft tissue sarcomas as they mature into adulthood.

Frequency
Soft tissue sarcomas are relatively uncommon cancers. They account for less than 1 % of all new cancer cases each year. In 2006, about 9,500 new cases were diagnosed in the United States. Soft tissue sarcomas are more commonly found in older patients (>50 years old) although in children and adolescents under age 20, certain histologies are common (rhabdomyosarcoma).

Symptoms
In their early stages, soft tissue sarcomas usually do not cause symptoms. Because soft tissue is relatively elastic, tumors can grow rather large, pushing aside normal tissue, before they are felt or cause any problems. The first noticeable symptom is usually a painless lump or swelling. As the tumor grows, it may cause other symptoms, such as pain or soreness, as it presses against nearby nerves and muscles. If in the abdomen it can cause abdominal pains commonly mistaken for menstrual cramps, indigestion, or cause constipation.

Diagnosis
The only reliable way to determine whether a soft tissue tumor is benign or malignant is through a biopsy. Therefore, all soft tissue lumps that persist or grow should be biopsied. A biopsy can be obtained via needle biopsy or with surgical biopsy. During this procedure, a doctor makes an incision or uses a special needle to remove a sample of tumor tissue. A pathologist examines the tissue under a microscope. If cancer is present, the pathologist can usually determine the type of cancer and its grade. The grade of the tumor is determined by how abnormal the cancer cells appear when examined under a microscope. The grade predicts the probable growth rate of the tumor and its tendency to spread. Low-grade sarcomas, although cancerous, are unlikely to metastasize. High-grade sarcomas are more likely to spread to other parts of the body.

Treatment
In general, treatment for soft tissue sarcomas depends on the stage of the cancer. The stage of the sarcoma is based on the size and grade of the tumor, and whether the cancer has spread to the lymph nodes or other parts of the body (metastasized). Treatment options for soft tissue sarcomas include surgery, radiation therapy, and chemotherapy.


 * Surgery is the most common treatment for soft tissue sarcomas. If possible, the doctor will remove the cancer and a safe margin of the healthy tissue around it. Depending on the size and location of the sarcoma, it may occasionally be necessary to remove all or part of an arm or leg (amputation). However, the need for amputation rarely arises; no more than 10 % to 15 % of individuals with sarcoma undergo amputation. In most cases, limb-sparing surgery is an option to avoid amputating the arm or leg. It is important to obtain a margin free of tumor to decrease the likelihood of local recurrence and give the best chance for eradication of the tumor.
 * Radiation therapy (treatment with x-rays or radioactive implants) may be used either before surgery to shrink tumors or after surgery to kill any cancer cells that may have been left behind. In some cases, it can be used to treat tumours that cannot be surgically removed. In multiple studies, radiation therapy has been found to improve the rate of local control, but has not had any influence on overall survival.
 * Chemotherapy (treatment with anticancer drugs) may be used with radiation therapy either before or after surgery to try to shrink the tumor or kill any remaining cancer cells. In general, chemotherapy effects for soft tissue sarcoma have had little impact as opposed to other cancers.  If the cancer has spread to other areas of the body, chemotherapy may be used to shrink tumors and reduce the pain and discomfort they cause, but is unlikely to eradicate the disease. The use of chemotherapy to prevent the spread of soft tissue sarcomas has not been proven to be effective. Patients with soft tissue sarcomas usually receive chemotherapy intravenously (injected into a blood vessel).

Doctors are conducting clinical trials in the hope of finding new, more effective treatments for soft tissue sarcomas, and better ways to use current treatments. Clinical trials are in progress at hospitals and cancer centers around the country. Clinical trials are an important part of the development of new methods of treatment. Before a new treatment can be recommended for general use, doctors conduct clinical trials to find out whether the treatment is safe for patients and effective against the disease.

Tables
An earlier version of this article was taken from the United States National Cancer Center's Cancer Information Service.