What Is It?
Soft-tissue sarcomas are cancerous tumors that start in either of two types of primitive (immature) cells: nerve cells and mesenchymal cells. These cells usually develop into muscle, fat, cartilage or other structural tissues. Rarely, instead of maturing, these immature cells transform into abnormal, aggressive cells that multiply out of control to form a cancerous tumor.
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 (contains lipid) 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. Example are neurofibrosarcoma or ectomesenchymoma. A soft-tissue sarcoma that doesn’t resemble any type of normal soft tissue is called “undifferentiated” or “unclassified”.
About 60 percent of soft-tissue sarcomas develop in the arms and legs, 30 percent in the trunk of the body and 10 percent in the head and neck. In the United States, soft-tissue sarcomas account for less than 1 percent of all cancers, but almost 7 percent of all cancers in children. Approximately 8,100 new cases are diagnosed each year in the United States. About one-fifth of those occur in children and most occur in adults over age 55. Among children, soft-tissue sarcomas are two times more common in whites than in African-Americans.
As a group, soft-tissue sarcomas have been linked to a wide 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.
- Environmental exposure — 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, vinyl chloride and, possibly, marijuana and cocaine.
- Biological factors — 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. Sarcomas are also more common in people with certain genetic (inherited) syndromes, particularly Li-Fraumeni syndrome and neurofibromatosis type I.
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 that all the other 19 types. 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.
Rhabdomyosarcoma is the most common form of soft-tissue cancer in children, accounting for 5 percent to 8 percent of all childhood cancers. It typically appears in one of three locations: in the head and neck region, in the urinary tract and reproductive organs, or in 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-teen-age 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 percent 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.
Other Soft-Tissue Sarcomas (Children And Adults)
Many other types of sarcomas can occur in fatty tissues, fibrous tissues, blood vessels, nerves, tissues in joints, and smooth muscles. Some of the most frequently diagnosed types include:
- Malignant fibrous histiocytoma — This sarcoma starts in either primitive immune cells called histiocytes or from 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. Malignant fibrous histiocytoma 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, a few have been linked to Paget’s disease, to bone damage caused by interruption of the bone’s blood supply, or to 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, at the back of the abdomen, and it rarely spreads.
- Fibrosarcoma — The 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 the cells that line 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, and it usually arises in the trunk or extremities.
- Angiosarcoma — Under a microscope, this tumor most closely resembles the tissue of blood vessels. An angiosarcoma may start in many different locations, including muscles, skin, liver, breast and bones. It usually occurs in adults, especially those with a history of exposure to vinyl chloride.
- Leiomyosarcoma — Cells of this tumor most closely resemble those of smooth muscle. Leiomyosarcoma commonly develops in the gastrointestinal tract, especially in people with weakened immune defenses because of AIDS or other conditions that deplete immune defenses.
In adults, 40 percent of sarcomas are malignant fibrous histiocytomas, and 25 percent of sarcomas 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 some part of the trunk. This lump may or may not be painful. In physically active individuals, the lump caused by a soft-tissue sarcoma 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:
- Within the eye or eyelid, rhabdomyosarcoma can cause a bulging eye, a swollen eyelid or paralysis of the eye muscles.
- In the sinuses, rhabdomyosarcoma can cause a stuffy or blocked nose, sometimes together with a nasal discharge that contains pus or blood.
- Deep in the skull, rhabdomyosarcoma 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, rhabdomyosarcoma 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.
After reviewing your symptoms, your doctor will perform a thorough physical examination with special attention to the lump and the area around it. After that, the first step may involve a series of X-rays of the involved area. Usually, a Computed tomography (CT) scan or magnetic resonance imaging (MRI) scan also will be done to provide a more detailed view of the tumor. Your doctor also may order basic blood and urine tests as part of your general health evaluation. Ultimately, you also will need a biopsy of the affected area to confirm the diagnosis of soft-tissue sarcoma and to determine the specific variety of sarcoma. A biopsy sample can be obtained through a needle in some cases, or it may be obtained through surgery. The sample of tissue is examined in a laboratory.
If diagnostic tests show signs of a cancerous tumor, your doctor will refer you to a major medical center that has the facilities, personnel and experience to treat cancer. Tests there will check whether the cancer has spread to areas away from where it began, and may include a chest X-ray, a chest CT scan, a radionuclide bone scan, a bone-marrow biopsy, or other tests.
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.
There is no proven way to prevent most cases of soft-tissue sarcoma. However, since 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 intravenous drug use. 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 equipment available to reduce your exposure, then use this equipment consistently while you are on the job. If you need more information about specific types of exposures or specific protective equipment, contact the National Institute for Occupational Safety and Health, which is part of the U.S. Centers for Disease Control and Prevention.
Once your doctor has confirmed 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 tumor histologic 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 the cancer can be shown to have spread to nearby lymph nodes or to distant organs.
- Another system, called the French Federation of Cancer Centers [FNCLCC] system, uses the microscope appearance of tumor tissue to predict (with reasonable accuracy) the likelihood that the cancer already has spread (metastisized), even when it is not detectable by other tests. 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, presence of metastases, and whether (either by expansion of the original tumor mass or by metastasis) the tumor has extended beyond the region of the skeleton where it originated. Since muscle groups in the skeleton are divided into separate compartments by “sleeves” of connecting tissue, growth or spread beyond the compartment of origin can be evidence that a tumor is growing aggressively.
For most soft-tissue sarcomas, the basic treatment is to surgically remove the entire tumor, along with a generous margin of noncancerous tissue. This is called wide excision. After surgery, further treatment usually depends on the specific type of sarcoma, the tumor stage and grade, tumor location, and the patient’s age and general health. Tumor grade is especially important, since 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) tend to spread to distant areas of the body. On the other hand, “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 adequately treated.
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 with metastasis. In the eye, rhabdomyosarcoma usually is treated with radiation and chemotherapy, without removal of 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 in 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.
When To Call A Professional
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.
In addition, if you are a parent, call your doctor promptly if your child develops symptoms of rhabdomyosarcoma of the head, neck or urinary tract or reproductive organs.
In general, 75 percent of people with localized soft-tissue sarcomas will survive for at least five years after diagnosis, and many will survive much longer, provided that the sarcoma can be removed completely and has a favorable tumor grade. Patients with sarcomas that have metastasized have a much poorer prognosis, with five-year survival rates of 20 percent or less.
For children with localized rhabdomyosarcoma, long-term survival rates of up to 90 percent 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 percent of children having long-term survival if there are no metastases and 20 percent of children having long-term survival if cancer has become metastatic. 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 percent 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 metastasized have a very low chance of surviving five years or longer.
For malignant fibrous histiocytoma, the National Cancer Institute reports an overall five-year survival rate of 59 percent for patients whose tumors could be removed completely with surgery after chemotherapy. Similarly, the overall five-year survival rate for fibrosarcoma is about 60 percent. For patients with angiosarcoma, the five-year survival is 12 percent.
Certain proteins in the blood may help to predict how aggressive a soft-tissue sarcoma is. These proteins, called growth factors and endostatin, are a subject of active research because there is hope that they might become targets of treatment for soft-tissue sarcoma.
Diseases and Conditions Center
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.