Cancers that arise from the soft tissues such as muscle, fat, nerve, cartilage or blood vessel are called sarcomas. Cancers that arise from bone are also classified as sarcomas. Many soft tissue sarcomas are quite fleshy in appearance. The cells that make up these soft tissues may become cancerous. Scientists do not yet fully understand the reasons why these soft tissue cells become cancerous, although there may be some genetic abnormalities associated with soft tissue sarcomas as well as other contributing factors listed below.

In many cases, the tumor contains cancer cells that still look somewhat like normal soft tissue when viewed under a microscope. The tumor is named according to the type of soft tissue it resembles. For example, a soft tissue sarcoma that looks like fat is called a liposarcoma, while a tumor that looks like fibrous tissue is called a fibrosarcoma. If a soft tissue sarcoma resembles more than one type of soft tissue, its name will reflect its complex appearance, such as neurofibrosarcoma. A soft tissue sarcoma that doesn't resemble any type of normal tissue is called undifferentiated or unclassified. Although not arising from soft tissues, sarcomas arising from the bone are called osteosarcomas.

About 60% of soft tissue sarcomas develop in the arms and legs, 30% in the trunk of the body, and 10% in the head and neck. In the United States, soft tissue sarcomas account for less than 1% of all cancers, but almost 7% of all cancers in children. More than 8,000 new cases are diagnosed each year in the United States. About one-fifth occur in children. Most occur in adults over age 55. Among children, soft tissue sarcomas are two times more common in whites than in African-Americans.

Soft tissue sarcomas have been associated with a variety of environmental and biological factors, including:

• Previous local injury � Soft tissue sarcomas can form in areas of scar tissue from surgery, burns, fractures or radiation treatments.



• Exposure to chemicals � The risk of developing a soft tissue sarcoma increases in people who have been exposed to certain cancer causing agents (carcinogens), particularly polycyclic hydrocarbons, asbestos, dioxin and vinyl chloride. The strongest association is with vinyl chloride.



• Diseases or conditions � The risk of sarcoma increases in people who have weakened immune defenses because of an HIV (human immunodeficiency virus) infection, a congenital (inborn) immune deficiency or treatment with medications that suppress the immune system. A particular type of sarcoma, called Kaposi's sarcoma may be associated with HIV infection, although not all cases have this association.

Sarcomas are more common in people with certain genetic (inherited) syndromes, particularly Li-Fraumeni syndrome and neurofibromatosis type I. These are genetic diseases that are characterized by the presence of multiple types of cancers or sarcomas within the same individual.

Doctors have identified about 20 different types of soft tissue sarcomas on the basis of how the tumor cells appear when viewed under a microscope. Of these, rhabdomyosarcoma accounts for more cases of soft tissue sarcoma than all the other 19 types combined. Some doctors, therefore, separate childhood soft tissue sarcomas into two distinct groups: rhabdomyosarcoma and all other types. These groupings are not used for soft tissue sarcomas affecting adults.

Childhood Rhabdomyosarcoma
Rhabdomyosarcoma is the most common form of soft tissue cancer in children, accounting for 5% to 8% of all childhood cancers. It typically appears in one of three locations: in the head and neck region, the urinary tract and reproductive organs, or the arms and legs. In about two-thirds of cases, rhabdomyosarcoma occurs in a child who is age 6 or younger. Less often, it occurs during the early to mid-teenage years or, rarely, in adulthood. Under the microscope, the cells of a rhabdomyosarcoma tumor look like primitive muscle, similar to the immature muscle cells of a developing fetus.

Based on subtle differences in the tumor's microscopic appearance, several varieties of rhabdomyosarcoma are classified. The two most common varieties, embryonal and alveolar, account for at least 80% of all rhabdomyosarcoma tumors. In general, embryonal rhabdomyosarcoma tends to be a localized cancer that responds well to treatment and rarely spreads (metastasizes) away from the site where it started, while alveolar rhabdomyosarcoma tends to be aggressive and hard to treat. However, all soft tissue sarcomas have the ability to metastasize, even though some varieties do so less commonly. The most common place where sarcomas spread to is the lung.

Other Soft Tissue Sarcomas (Children and Adults)
Many other types of sarcomas can occur in fatty tissues, fibrous tissues, blood vessels, nerves, smooth muscles and tissues in joints. Some of the most frequently diagnosed types include:

• Malignant fibrous histiocytoma � This sarcoma starts in either a type of primitive immune cells called histiocytes or in cells that make fibrous (connecting) tissue. It usually appears as an area of bone destruction on X-rays. It occurs primarily in adults, and affects men more often than women. It typically begins in the long bones of the arms and legs, especially around the knee, and it tends to spread rapidly. Although most cases develop for unknown reasons, some cases may be triggered by a bone condition called Paget's disease, may occur after bone damage caused by interruption of the bone's blood supply, or may be a consequence of radiation treatment for prior cancers.



• Liposarcoma � This sarcoma has cells that resemble fat. Liposarcoma tends to arise in the arms, legs or in the area near the kidneys and at the back of the abdomen. It rarely spreads, but can continue to recur at the place where it first began, despite resection. This is called a local recurrence and generally represents tumor regrowth or growth of cells that were not recognized or adequately removed at the initial diagnosis.



• Kaposi's sarcoma � This tumor begins in the skin, mouth or digestive tract, or in the airways of the lungs. It occurs 15 times more often in men than in women. The tumor contains blood vessels and blood so it looks like one or more pink, purple or blue lumps. It is common in men who have HIV that is not being treated with antiviral medicines, or who have a suppressed immune system after an organ transplant and who also are infected with human herpes virus 8 (HHV-8). HHV-8 is a virus that has been blamed as a trigger for several varieties of cancer. Kaposi's sarcoma also occurs in men from the Mediterranean region and Africa and who do not have HIV.



• Fibrosarcoma � Cells of this tumor most closely resemble those of fibrous (connecting) tissue. Fibrosarcomas tend to occur in the arms, legs or trunk of infants less than 12 months old.



• Synovial sarcoma � Under a microscope, this tumor resembles cells that line the joints. It is marked by the presence of a specific chromosome change within the cancer cells. According to some cancer experts, synovial sarcoma is the second most common sarcoma in children. It tends to occur in either the knee or thigh of a person under the age of 30.



• Neurofibrosarcoma � This tumor, also known as a malignant peripheral nerve-sheath tumor, resembles the protective cells that normally cover nerves. Neurofibrosarcoma most commonly affects people with a disease called neurofibromatosis type I. It usually appears in the trunk or extremities.



• Angiosarcoma � Under a microscope, this tumor most closely resembles the tissue of blood vessels. An angiosarcoma may start almost anywhere on the body, especially in a muscle, the skin, the liver, a breast or bone. It usually occurs in adults, especially those with a history of exposure to vinyl chloride. The specific type of sarcoma associated with vinyl chloride arises in the liver, a so called hepatic angiosarcoma.



• Leiomyosarcoma � Cells of this tumor most closely resemble those of smooth muscle. Smooth muscle cells are the cells that move your hollow organs, such as when your intestines squeeze to move food. Leiomyosarcoma commonly develops in the gastrointestinal tract, especially in people with weakened immune defenses because of AIDS or other conditions that deplete immune defenses.
• Gastrointestinal stromal tumor (GIST) � These are tumors arising from the gastrointestinal tract that are considered sarcomas and have been associated with specific genetic abnormalities. More recently, the genetic abnormality that leads to the production of an abnormal substance has been shown to be the cause of the cancer. A new medicine has been targeted that neutralizes the genetic abnormality and can lead to improvements and in some cases, reversal and cure of the GIST.

In adults, 40% of sarcomas are malignant fibrous histiocytomas; 25% are liposarcomas.

In most cases, someone with soft tissue sarcoma will complain of a new, mysterious and persistent lump in some part of the body, most commonly on an arm, leg or trunk. This lump may or may not be painful. In people who are physically active, the lump is sometimes mistaken for an injury related to sports or recreational activities.

Rhabdomyosarcoma that does not involve the arms and legs can cause a painless lump in the head or neck, or it can cause other symptoms that reflect the tumor's location. For example:

• In the eye or eyelid, rhabdomyosarcoma can cause a bulging eye, a swollen eyelid or paralysis of the eye muscles.
• In the sinuses, it can cause a stuffy or blocked nose, sometimes together with a nasal discharge that contains pus or blood.
• Deep in the skull, it can erode the bones that protect the brain, triggering headache and nausea as the tumor gradually grows toward the brain's surface.
• In the urinary tract and reproductive organs, it can cause difficulty urinating, blood in the urine, constipation, a lump or mass inside the vagina, a vaginal discharge that contains blood and mucus, or a painless enlargement of one side of the scrotum with involvement of the testicle.

After reviewing your symptoms, your doctor will thoroughly examine you, paying special attention to the lump and the area around it. After that, you may need a series of X-rays. Usually, a computed tomography (CT) scan or magnetic resonance imaging (MRI) scan will provide a detailed view of the tumor. Your doctor may order basic blood and urine tests as part of your general health evaluation. Ultimately, you will need a biopsy to confirm the diagnosis of soft tissue sarcoma and to determine the specific variety. A biopsy sample can be obtained through a needle in some cases or it may be obtained through surgery. The tissue sample is processed so it can be examined under the microscope by a pathologist. One of the most important aspects of the analysis of the sarcoma is its appearance under the microscope. The pathologist can determine how active the sarcoma is by estimating the number of dividing cells (mitoses) in the specimen. Those cancers with a large number of mitoses carry a worse prognosis and may require more aggressive treatments.

If diagnostic tests show signs of a cancerous tumor, your doctor will refer you to a medical center that has the facilities, personnel and experience to treat cancer. Tests to check whether the cancer has spread may include a chest X-ray, a chest CT scan, a radionuclide bone scan, bone marrow biopsy or other tests. A test called a positron emission tomography scan (PET scan) is now used sometimes to examine the body for tissue areas that are growing, since it may help to identify a spreading tumor. This test is new, so doctors are still uncertain how helpful results from PET scans may be in guiding cancer treatment. However, recent evidence suggests that the use of a PET scan, in association with conventional CT scans may provide a more accurate estimate of the cancer location.

A soft tissue sarcoma will continue to grow until it is treated. Without proper treatment, some soft tissue sarcomas eventually spread to the lungs, lymph nodes or other parts of the body. It is especially important to have the sarcoma removed with the largest rim of normal tissue as practical. Sarcomas can recur locally, and the likelihood of having a local recurrence may be lessened with a wide surgical excision at the time of the removal of the tumor.

There is no proven way to prevent most cases of soft tissue sarcoma. However, because HIV infection seems to increase the risk of some sarcomas, you might be able to reduce your risk by avoiding behaviors that can lead to HIV, such as unsafe sex and illegal use of intravenous drugs (injected into a vein). If you are a woman, having your first pregnancy at a later age may put you at a slightly higher risk of developing soft tissue sarcoma.

If your occupation exposes you to substances that can cause soft tissue sarcomas, find out about the types of protective measures available to reduce your exposure, and then use those measures consistently while on the job. If you need more information about specific types of exposures or specific protective measures and equipment, contact the National Institute for Occupational Safety and Health (NIOSH), which is part of the U.S. Centers for Disease Control and Prevention (CDC).

Once your doctor confirms that you have a soft tissue sarcoma, the next step is to determine the tumor stage, which indicates how far the tumor has spread, if at all. Currently, several different systems are used:

• The American Joint Commission on Cancer determines stage by the tumor's grade (roughly, an assessment of how abnormal tumor cells appear under the microscope, and how aggressive the cancer is likely to be), tumor size, and whether or not tests show that the cancer has spread to nearby lymph nodes or to distant organs.



• The French Federation of Cancer Centers system uses the microscope appearance of tumor tissue to predict (with reasonable accuracy) the likelihood that the cancer already has spread (metastasized), even when other tests are unable to detect that the cancer has spread. A high likelihood of metastasis can influence the treatment that is recommended.



• The Musculoskeletal Tumor Society Staging System assigns tumor stage on the basis of tumor grade (determined by its appearance under a microscope), presence of metastases, and whether the tumor has extended beyond the region of the skeleton where it began. Because muscle groups in the skeleton are divided into separate compartments by "sleeves" of connecting tissue, any growth or spread beyond the compartment of origin can be evidence that a tumor is spreading aggressively.

For most soft tissue sarcomas, surgery is the basic treatment. The entire tumor is removed, along with a generous margin of noncancerous tissue surrounding the tumor. This is called wide excision. After surgery, further treatment usually depends on the type of sarcoma, the tumor stage and grade, tumor location, and the person's age and general health. Tumor grade is especially important because it often is the key to the tumor's current spread and future behavior. For example, high-grade soft tissue sarcomas (sarcomas containing areas of very abnormal cells and tissue destruction or having a large number of mitoses) tend to spread to distant areas of the body. Low-grade soft tissue sarcomas (sarcomas that more closely resemble normal cells under the microscope) are less likely to spread, but they may come back again if they are not completely treated.

Rhabdomyosarcoma
If rhabdomyosarcoma is located in an arm or leg, and all of the tumor can be removed surgically, surgery usually is followed by chemotherapy. However, if surgery fails to remove the entire tumor, further treatment with both radiation and chemotherapy usually follows. Chemotherapy and radiation also are used to treat rhabdomyosarcomas that have spread to other parts of the body. In the eye, rhabdomyosarcoma usually is treated with radiation and chemotherapy, without removing the eye. For rhabdomyosarcomas in the bladder or female reproductive tract, chemotherapy and radiation are used to shrink the tumor before surgery, so that the surgeon can preserve as much of the affected organ as possible.

Other Soft Tissue Sarcomas
As with rhabdomyosarcoma, surgical removal is the treatment of choice. For fibrosarcoma, chemotherapy often is given before surgery to shrink the tumor before removing it. For synovial sarcoma, radiation treatments may be given after surgery, to destroy any remaining cancer cells. For angiosarcoma, which is particularly difficult to treat, some doctors try a combination of chemotherapy and radiation treatments.

Call your doctor promptly if you or anyone in your family develops a persistent lump or swelling anywhere in the body, especially on the arm, leg or trunk. Also, call your doctor is you have unexplained symptoms that might be caused by a growing lump, such as symptoms in the head or neck. It is especially important that the diagnosis of a sarcoma be confirmed by a pathologist who specializes in sarcomas. Because of the relative rarity of these tumors, and the many different types, a confirmatory diagnosis that includes the grade of the sarcoma and the mitotic rate is very important for selecting the correct treatment. Some specialist patholgists are also performing detailed analyses of the genes that are involved in these sarcomas which can aid in the diagnosis for some of the more undifferentiated varieties.

In general, 75% of people with localized soft tissue sarcomas will survive for at least 5 years after diagnosis. Many will survive much longer, provided that the sarcoma can be removed completely and has a favorable tumor grade. People with sarcomas that have spread have a much poorer prognosis, with 5-year survival rates of 20% or less.

For children with localized rhabdomyosarcoma, long-term survival rates of up to 90% are possible, provided surgery can remove the entire tumor. If the tumor cannot be removed entirely, the long-term survival rate is lower, with about 65% of children having long-term survival if the cancer hasn't spread, and 20% of children having long-term survival if the cancer has spread. In general, children with embryonal rhabdomyosarcoma respond better to treatment than those with the alveolar type.

For adults with rhabdomyosarcoma, long-term survival is predicted for 60% of people whose tumors are localized and less than 5 centimeters in diameter at the time of treatment. People with larger rhabdomyosarcoma cancers or ones that have spread to other parts of the body have a very low chance of surviving five years or longer.

For malignant fibrous histiocytoma, the National Cancer Institute (NCI) reports a 5-year survival rate of 59% for people whose tumors could be removed completely with surgery after chemotherapy. The 5-year survival rate for fibrosarcoma is about 60%. For people with angiosarcoma, the 5-year survival is 12%.

Certain proteins in the blood may help to predict how aggressive a soft tissue sarcoma is. These proteins, called growth factors, are a subject of active research because there is hope that they might become targets of treatment for soft tissue sarcoma. There is now real excitement in trying to further understand what causes these sarcomas and what makes them grow and metastasize. Since the finding of the specific abnormality in GIST tumors, researchers are evaluating the many complex biochemical reactions that occur in a sarcoma and trying to devise new medicines that can block the abnormal reactions. This type of development of new medicines is called "targeted therapy" where the specific chemical reaction for the cancer cell is identified; a drug is developed that effects the reaction; and the patient is treated with the drug, leading to improved treatment results. Only a few years ago, this approach was thought to be improbable. It is now a reality for one type of sarcoma and several other types of cancers.

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