How are soft tissue sarcomas diagnosed?
If you have signs or symptoms or other reasons to suggest you might have a sarcoma, your doctor will talk with you, examine you, and probably need to order some tests to find out if you have cancer.
Some tests, such as a computed tomography (CT) scan or a magnetic resonance imaging (MRI) scan, are often done to look for the cause of symptoms and to find a tumor (such as a sarcoma). Other tests may be done after a sarcoma is diagnosed to look for cancer spread.
A regular x-ray of the area with the lump may be the first test ordered. A chest x-ray may be done after you are diagnosed to see if the sarcoma has spread to the lungs.
Computed tomography scans
The CT scan is an x-ray procedure that produces detailed, cross-sectional images of your body. Instead of taking one picture like a conventional x-ray, a CT scanner takes many pictures as it rotates around you. A computer then combines these pictures into an image of a slice of your body. The machine will create multiple images of the part of your body being studied. A CT scan is often done if the doctor suspects a soft tissue sarcoma in the chest, abdomen, or the retroperitoneum (the of the abdomen) . This test is also used to see if the sarcoma has spread into the lungs, liver or other organs.
A CT scanner has been described as a large donut, with a narrow table in the middle opening. You will need to lie still on the table while the scan is being done. CT scans take longer than regular x-rays, and you might feel a bit confined by the ring while the pictures are being taken
Before any pictures are taken, you might be asked to drink 1 to 2 pints of a liquid called oral contrast. This helps outline the intestine more clearly. You may also receive an IV (intravenous) line through which a different kind of contrast dye (IV contrast) is injected. This helps better outline structures in your body.
The IV contrast dye can also cause some flushing (redness and warm feeling). Some people are allergic and get hives or, rarely, have more serious reactions like trouble breathing and low blood pressure. Be sure to tell the doctor if you have ever had a reaction to any contrast material used for x-rays.
CT scans might be done to precisely guide a biopsy needle into a tumor inside the body — the chest or abdomen, for example. For this procedure, called a CT-guided needle biopsy, the patient remains on the CT scanning table while a radiologist advances a biopsy needle toward the location of the mass. CT scans are repeated until the doctors are sure the needle is within the mass.
Magnetic resonance imaging scans
Magnetic resonance imaging (MRI) scans use radio waves and strong magnets instead of x-rays to take pictures of the body. The energy from the radio waves is absorbed and then released in a pattern formed by the type of tissue and by certain diseases. A computer translates the pattern of radio waves given off by the tissues into a very detailed image of parts of the body. A contrast material might be injected, just as with CT scans, but is used less often.
MRI scans are often part of the work-up of any tumor that could be a sarcoma. They are often better than CT scans in evaluating sarcomas in the arms or legs. They provide a good picture of the extent of the tumor. They can show your health care team many things about the tumor, including location, size, and sometimes even the type of tissue it comes from (like fat or muscle). This makes MRI scans useful in planning a biopsy.
MRIs are also very helpful in examining the brain and spinal cord.
MRI scans are a little more uncomfortable than CT scans. First, they take longer — often up to an hour. Also, you have to lie inside a long tube, which is confining and can be upsetting. Special "open" MRI machines sometimes are an option for people who have claustrophobia (fear of enclosed spaces), but the drawback is that the pictures are often not as clear. MRI machines also make a thumping noise that you may find disturbing. Some places will provide headphones with music to block this noise out.
Ultrasound uses sound waves and their echoes to produce pictures of parts of the body. A small instrument called a transducer emits sound waves and picks up the echoes as they bounce off the organs. A computer converts the sound wave echoes into an image that is displayed on a computer screen.
This is a very easy procedure to have. It uses no radiation, which is why it is often used to look at developing fetuses. For most ultrasounds, you simply lie on a table while a technician moves the transducer over the part of your body being examined. Usually, the skin is first lubricated with gel. Ultrasound may be done before a biopsy to see if a lump is a cyst, meaning if it has fluid and is likely benign, or if it is solid and more likely a tumor. This test is often not needed if a CT or MRI was done.
Positron emission tomography scan
In this test, radioactive glucose (sugar) is injected into the patient's vein to look for cancer cells. Because cancers use glucose (sugar) at a higher rate than normal tissues, the radioactivity will tend to concentrate in the cancer. A scanner can spot the radioactive deposits. A positron emission tomography (PET) scan is useful when your doctor thinks the cancer has spread but doesn't know where. A PET scan can be used instead of several different x-rays because it scans your whole body. Often the PET scan is used with a CT scan. This helps decide if abnormalities seen on the CT scan are cancer or something else. PET is not often used for sarcoma, but it can be helpful in certain cases.
A biopsy is a procedure that removes a sample of tissue from a tumor to see if it is cancer. The piece of tissue is looked at under a microscope and, some other tests may be done on the sample as well. A physical exam or imaging test may suggest that a tumor is a sarcoma, but a biopsy is the only way to be certain that it is a sarcoma and not another type of cancer or a benign disease.
Several types of biopsies are used to diagnose sarcomas. Doctors experienced with these tumors will choose one, based on the size and location of the tumor. Most prefer to use a fine needle aspiration or a core needle biopsy as the first step.
Fine needle aspiration (FNA) biopsy
In FNA, the doctor uses a very thin needle and a syringe to withdraw small pieces of tissue from the tumor mass. The doctor can often aim the needle while feeling the mass near the surface of the body. If the tumor is too deep to feel, the doctor can guide the needle while viewing it on a computed tomography (CT) scan or ultrasound. The main advantage of FNA is that it can be used to biopsy tumors deep in the body without surgery. The disadvantage is that the thin needle may not remove enough tissue to make a precise diagnosis.
FNA is often useful in showing that a mass first thought to be a sarcoma (found on physical exam or imaging tests) is really another type of cancer, a benign tumor, an infection, or some other disease. But if FNA results suggest a sarcoma, another type of biopsy will usually be done to remove enough tissue to confirm that diagnosis. After a sarcoma is diagnosed, FNA is most useful in determining whether additional tumors in other organs are metastases.
Core needle biopsy
Core needle biopsies use a needle that is larger than the FNA needle. Sometimes this needle is called a Tru-Cut needle. It removes a cylindrical piece of tissue about 1/16 inch across and 1/2 inch long. It usually removes enough tissue to see if a sarcoma is present. Like FNA, CT scan and ultrasound can be used to guide the needle into tumors of internal organs.
In a surgical biopsy, the entire tumor or a piece of the tumor is removed during an operation. There are 2 types of surgical biopsies, excisional and incisional. In an excisional biopsy, the surgeon removes the entire tumor. In an incisional biopsy, only a piece of a large tumor is removed. An incisional biopsy almost always removes enough tissue to diagnose the exact type and grade of sarcoma. If the tumor is near the skin surface, this is a simple operation that can be done with local or regional anesthesia (numbing medication given near the mass or into a nerve). But if the tumor is deep inside the body, general anesthesia is used (the patient is asleep).
If a tumor is rather small, near the surface of the body, and not located near critical tissues (such as important nerves or large blood vessels), the doctor may choose to remove the entire mass and a margin of normal tissue in an excisional biopsy. This surgery combines the biopsy and the treatment into one operation, so it should only be done by a surgeon with experience in treating sarcomas.
If the tumor is large, then an incisional biopsy is needed. Only a surgeon experienced in sarcoma treatment should perform this procedure.
You might want to ask about your surgeon’s experience with this procedure. Proper biopsy technique is a very important part of successfully treating soft tissue sarcomas. An improper biopsy can lead to tumor spread and problems removing the tumor later on. An incisional biopsy in the wrong place or an excision without wide enough margins can make it harder to completely remove a sarcoma later on. To prevent these problems, these 2 types of biopsies should only be done by a surgeon experienced in treating sarcomas. It is best that an incisional biopsy be done by the same surgeon who will later remove the entire tumor (if a sarcoma is found).
Testing biopsy samples
The tissue removed will be looked at under the microscope to see if cancer is present. If it is, the doctor will try to determine what kind it is (sarcoma or carcinoma).
Grading: If a sarcoma is present, the biopsy will be used to determine what type it is and its grade. The grade of a sarcoma is based on how the cancer cells look under the microscope. In grading a cancer, the pathologist (a doctor who specializes in diagnosing diseases by looking at the tissue under a microscope) considers how closely the tumor resembles normal tissue (differentiation), how many of the cells appear to be dividing, and how much of the tumor is made up of dying tissue.
Each factor is given a score, and the scores are added to determine the grade of the tumor. Sarcomas that have cells that look more normal and have fewer cells dividing are generally placed in a low-grade category. Low-grade tumors tend to be slow growing, slower to spread, and often have a better outlook (prognosis) than higher-grade tumors. Certain types of sarcoma are automatically given higher differentiation scores. This affects the overall score so much that they are never considered low grade. Examples of these include synovial sarcomas and embryonal sarcomas.
The grade is partly used to determine the stage of a sarcoma. The official staging system (see the section “How are soft tissue sarcomas staged?”) divides sarcomas into 3 grades (1 to 3). The grade of a sarcoma helps predict how rapidly it will grow and spread. It is useful in predicting a patient's outlook and helps determine treatment options.
Immunohistochemistry: Sometimes these special tests are needed to accurately determine whether a sarcoma is present and, if so, what type. Part of the biopsy sample is treated with special man-made antibodies that recognize cell proteins typical of certain kinds of sarcomas. The cells are treated with chemicals that make the cells containing these specific proteins change color. The color change is then seen under a microscope.
Cytogenetics: For this test, cells' chromosomes are examined with a microscope to look for changes. For example, in certain types of sarcomas part of one chromosome may be abnormally attached to part of a different chromosome (called a translocation). To see the chromosomes clearly, the cancer cells must be grown in laboratory dishes until they start dividing. This can take a week or more.
Fluorescent in situ hybridization (FISH) can sometimes be used to detect translocations and other chromosome changes without first growing the cells in the lab. Tests of chromosome changes are not required to diagnose a sarcoma, but they are sometimes very useful in confirming that a certain type of sarcoma is present. And as new changes are discovered, these tests may become more important and more common.
Reverse transcription polymerase chain reaction (RT-PCR): This test is another way to find translocations in some sarcomas (such as the Ewing family of tumors, alveolar rhabdomyosarcoma, and synovial sarcoma) to confirm the type of tumor. Instead of using a microscope to look for the chromosome changes as in cytogenetic testing or FISH, RT-PCR uses chemical analysis of the RNA (a substance that is made from DNA) from genes affected by the translocation. RT-PCR testing is often able to find translocations that aren't detected by cytogenetics.
Last Medical Review: 12/29/2014
Last Revised: 02/09/2016