Sarcoma is a type of cancer that develops in bones or soft tissues. Your soft tissue includes:
- blood vessels
- fibrous tissue
- the lower layers of the skin (not the outer layer)
- the lining of the joints
Several types of abnormal growths can occur in soft tissue. If a growth is a sarcoma, then it’s a malignant tumor or cancer. Malignant means that parts of the tumor can break off and spread into surrounding tissues. These escaped cells move throughout the body and lodge in the liver, lungs, brain, or other important organs.
Sarcomas of soft tissue are relatively uncommon, especially when compared with carcinomas, another type of malignant tumor. Sarcomas can be life-threatening, especially if they’re diagnosed when a tumor is already large or has spread to other tissues.
Soft tissue sarcomas are most often found in the arms or legs, but can also be found in the trunk, internal organs, head and neck, and the back of the abdominal cavity.
There are many kinds of soft tissue sarcomas. A sarcoma is categorized by the tissue in which it has grown:
- Malignant tumors in fat are called liposarcomas.
- In smooth muscle around internal organs, cancerous sarcomas are known as leiomyosarcomas.
- Rhabdomyosarcomas are malignant tumors in skeletal muscle. Skeletal muscle is located in your arms, legs, and other areas of the body. This type of muscle enables movement.
- Gastrointestinal stromal tumors (GISTs) are malignancies that begin in the gastrointestinal (GI) tract, or digestive tract.
Although they also occur in adults, rhabdomyosarcomas are the most common soft tissue sarcomas in children and adolescents.
Other soft tissue sarcomas that are very rare include:
- malignant schwannomas
- neurogenic sarcomas
- synovial sarcomas
- Kaposi sarcomas
- malignant mesenchymomas
- alveolar soft part sarcomas
- epithelioid sarcomas
- clear cell sarcomas
- pleomorphic undifferentiated sarcomas
- spindle cell tumors
In its early stages, a soft tissue sarcoma may not cause any symptoms. A painless lump or mass under the skin of your arm or leg may be the first sign of a soft tissue sarcoma. If a soft tissue sarcoma develops in your stomach, it may not be discovered until it’s very large and pressing on other structures. You may have pain or breathing difficulties from a tumor pushing on your lungs.
Another possible symptom is an intestinal blockage. This can occur if a soft tissue tumor is growing in your stomach. The tumor pushes too hard against your intestines and prevents food from moving through easily. Other symptoms include blood in stool or vomit or black, tarry stools.
Usually, the cause of a soft tissue sarcoma isn’t identified.
The exception to this is Kaposi sarcoma. Kaposi sarcoma is a cancer of the lining of blood or lymph vessels. This cancer causes purple or brown lesions on the skin. It’s due to infection with the human herpes virus 8 (HHV-8). It frequently occurs in people with reduced immune function, such as those infected with HIV, but it can also arise without HIV infection.
Genetic risk factors
Some inherited or acquired DNA mutations, or defects, can make you more prone to developing a soft tissue sarcoma:
- Basal cell nevus syndrome increases your risk of basal cell skin cancer, rhabdomyosarcoma, and fibrosarcoma.
- Inherited retinoblastoma causes a kind of childhood eye cancer, but it can also increase the risk of other soft tissue sarcomas.
- Li-Fraumeni syndrome increases the risk of many kinds of cancer, often from radiation exposure.
- Gardner’s syndrome leads to cancers in the stomach or bowel.
- Neurofibromatosis can cause nerve sheath tumors.
- Tuberous sclerosis can result in rhabdomyosarcoma.
- Werner’s syndrome can cause many health problems, including an increased risk of all soft tissue sarcomas.
Exposure to certain toxins, such as dioxin, vinyl chloride, arsenic, and herbicides that contain phenoxyacetic acid at high doses may increase your risk of developing soft tissue sarcomas.
Radiation exposure, especially from radiation therapy, can be a risk factor. Radiation therapy often treats more common cancers such as breast cancer, prostate cancer, or lymphomas. However, this effective therapy can increase your risk of developing certain other forms of cancer, such as a soft tissue sarcoma.
Doctors can usually only diagnose soft tissue sarcoma when the tumor becomes large enough to be noticed because there are very few early symptoms. By the time the cancer causes recognizable signs, it may already have spread to other tissues and organs in the body.
If your doctor suspects a soft tissue sarcoma, they’ll get a complete family history to see if other members of your family may have had any rare forms of cancer. You’ll also likely have a physical exam to check your general health. This may help determine the treatments that would be best for you.
Your doctor will study the tumor’s location using imaging scans such as simple X-rays or a CT scan. The CT scan may also involve using an injected dye to make the tumor easier to see. Your doctor may also order an MRI, PET scan, or an ultrasound.
Ultimately, a biopsy must confirm the diagnosis. This test usually involves inserting a needle into a tumor and removing a small sample.
In some cases, your doctor may use a scalpel to cut away part of the tumor so that it’s easier to examine. Other times, especially if the tumor is pressing on an important organ such as your intestines or lungs, your doctor will remove the entire tumor and surrounding lymph nodes.
The tissue from the tumor will be examined under a microscope to determine whether the tumor is benign or malignant. A benign tumor doesn’t invade other tissue, but a malignant tumor can.
Some other tests performed on a tumor sample from a biopsy include:
- immunohistochemistry, which looks for antigens or sites on tumor cells to which certain antibodies can attach
- cytogenic analysis, which looks for changes in the chromosomes of the tumor cells
- fluorescence in situ hybridization (FISH), a test to look for certain genes or short pieces of DNA
- flow cytometry, which is a test that looks at the number of cells, their health, and the presence of tumor markers on the surface of cells
Staging the cancer
If your biopsy confirms cancer, your doctor will grade and stage the cancer by looking at the cells under the microscope and comparing them to normal cells of that kind of tissue. Staging is based on the size of the tumor, the grade of the tumor (how likely it is to spread, ranked grade 1 [low] to grade 3 [high]), and whether the cancer has spread to lymph nodes or other sites. The following are the different stages:
- Stage 1A: tumor is 5 cm or less in size, grade 1, and the cancer has not spread to lymph nodes or distant sites
- Stage 1B: tumor is larger than 5 cm, grade 1, and the cancer has not spread to lymph nodes or distant sites
- Stage 2A: tumor is 5 cm or less, grade 2 or 3, and the cancer has not spread to lymph nodes or distant sites
- Stage 2B: tumor is larger than 5 cm, grade 2, and the cancer has not spread to lymph nodes or distant sites
- Stage 3A: tumor is larger than 5 cm, grade 3, and the cancer has not spread to lymph nodes or distant sites OR tumor is any size and cancer has spread to nearby lymph nodes but not other sites
- Stage 4: tumor is any size and any grade, and has spread to lymph nodes and/or to other sites
Soft tissue sarcomas are rare, and it’s best to seek treatment at a facility that’s familiar with your type of cancer.
Treatment depends on the location of the tumor and the exact cell type that the tumor originated from (for example, muscle, nerve, or fat). If the tumor has metastasized, or spread to other tissues, this also affects treatment.
Surgical treatment is the most common initial therapy. Your doctor will remove the tumor and some of the surrounding healthy tissue and test to see if some tumor cells may still be left in your body. If the tumor is in other known sites, your doctor can also remove those secondary tumors.
Your doctor may also need to remove surrounding lymph nodes, which are small organs of the immune system. Lymph nodes are often the first places where tumor cells spread.
In the past, doctors would often need to amputate a limb that had tumors. Now, the use of advanced surgical techniques, radiation, and chemotherapy can often save a limb. However, large tumors that affect major blood vessels and nerves may still require limb amputation.
The risks of surgery include:
- damage to nearby nerves
- reactions to anesthesia
Chemotherapy is also used to treat some soft tissue sarcomas. Chemotherapy is the use of toxic drugs to kill cells that divide and multiply rapidly, such as tumor cells. Chemotherapy also damages other cells that divide rapidly, such as bone marrow cells, the lining of your intestine, or hair follicles. This damage leads to many side effects. However, if cancer cells spread beyond the original tumor, chemotherapy may effectively kill them off before they begin to form new tumors and harm vital organs.
Chemotherapy doesn’t kill off all soft tissue sarcomas. However, chemotherapy regimens do effectively treat one of the most common sarcomas, rhabdomyosarcoma. Drugs such as doxorubicin (Adriamycin) and dactinomycin (Cosmegen) can also treat soft tissue sarcomas. There are many other drugs that are specific to the tissue type in which the tumor started.
In radiation therapy, high-energy beams of particles such as X-rays or gamma rays damage the DNA of cells. Rapidly dividing cells such as tumor cells are much more likely to die from this exposure than normal cells, though some normal cells will die as well. Sometimes doctors combine chemotherapy and radiation therapy to make each more effective and kill more tumor cells.
The side effects of chemotherapy and radiation include:
- weight loss
- hair loss
- nerve pain
- other side effects that are specific to each type of drug regimen
Complications from the tumor itself depend on the location and size of the tumor. The tumor may press on important structures such as the:
- blood vessels
The tumor may invade and damage nearby tissues as well. If the tumor metastasizes, meaning cells break off and end up in other locations such as the following, new tumors can grow in these organs:
In these locations, tumors can cause extensive and life-threatening damage.
Long-term survival from a soft tissue sarcoma depends on the specific type of sarcoma. Outlook also depends on how advanced the cancer is when first diagnosed.
Stage 1 cancer will likely be much easier to treat than stage 4 cancer, and has a higher survival rate. A tumor that’s small, hasn’t spread into surrounding tissues, and is in an easily accessible location, such as the forearm, will be easier to treat and remove completely with surgery.
A tumor that’s large, surrounded by many blood vessels (making surgery difficult), and has metastasized to the liver or lung is much harder to treat.
The chances of recovery depend on:
- the location of the tumor
- the cell type
- the grade and stage of the tumor
- whether or not the tumor can be surgically removed
- your age
- your health
- whether the tumor is recurrent or new
After initial diagnosis and treatment, you’ll need to see your doctor often for checkups even if the tumor is in remission, which means it’s not detectable or not growing. X-rays, CT scans, and MRI scans may be necessary to check if any tumor has recurred at its original site or other places in your body.