Tests for Rhabdomyosarcoma

Certain signs and symptoms might suggest that a person has rhabdomyosarcoma (RMS), but tests are needed to find out for sure.

Medical history and physical exam

If you or your child has symptoms that could be from RMS (or another type of tumor), the doctor will want to get a complete medical history to find out more about the symptoms.

The doctor will also do a physical exam to look for possible signs of RMS or other health problems. For example, the doctor might be able to see or feel an abnormal lump or swelling.

If the doctor suspects RMS (or another type of tumor), tests will be needed to find out. These might include imaging tests, biopsies, and/or lab tests.

Imaging tests

Imaging tests use x-rays, magnetic fields, radioactive substances, or sound waves to create pictures of the inside of the body. Imaging tests might be done for a number of reasons, including:

• To help find out if a suspicious area might be cancer
• To determine the extent of a tumor or learn how far a cancer has spread
• To help determine if treatment is working

People who have or might have RMS will get one or more of these tests.

Plain x-rays

X-rays are sometimes used to look for tumors, but they are best for looking at bones. They don’t show much detail in internal organs, so other imaging tests are usually more helpful when looking for soft tissue tumors such as RMS.

A chest x-ray is sometimes done to look for cancer that might have spread to the lungs, although it isn’t needed if a chest CT scan is being done.

Computed tomography (CT) scan

The CT scan combines many x-ray pictures to make detailed cross-sectional images of parts of the body, including soft tissues such as muscles. A contrast material may be injected into a vein before the scan to help see details better..

This test can often show a tumor in detail, including how large it is and if it has grown into nearby structures. It can also be used to look at nearby lymph nodes, as well as the lungs or other areas of the body where the cancer might have spread.

Magnetic resonance imaging (MRI) scan

MRI scans create detailed images using radio waves and strong magnets instead of x-rays, so there is no radiation involved. A contrast material called gadolinium may be injected into a vein before the scan to help see details better..

This test might be used instead of a CT scan to look at the tumor and the tissues around it. MRI is especially useful if the tumor is in certain parts of the body, such as the head and neck, an arm or leg, or the pelvis. MRI scans can help determine the exact extent of a tumor, because they can show the muscle, fat, and connective tissue around the tumor in great detail. This is important when planning surgery or radiation therapy. MRI is also very useful if the doctor is concerned about possible spread to the spinal cord or brain.

Bone scan

A bone scan can help show if a cancer has spread to the bones. This test is useful because it provides a picture of the entire skeleton at once.

For this test, a small amount of low-level radioactive material is injected into the blood and travels to the bones. A special camera can detect the radioactivity and creates a picture of the skeleton.

Areas of active bone changes attract the radioactivity and show up as “hot spots” on the scan. These areas may suggest cancer in an area, but other bone diseases can also cause the same pattern, so other tests such as plain x-rays or MRI scans, or even a bone biopsy might be needed.

(A bone scan might not be needed if a positron emission tomography [PET] scan is done, as the PET scan can often provide similar information.)

Positron emission tomography (PET) scan

For a PET scan, a radioactive substance (usually a type of sugar related to glucose, known as FDG) is injected into the blood. Because cancer cells grow quickly, they will absorb large amounts of the sugar. A special camera can then create a picture of areas of radioactivity in the body. The picture is not detailed like a CT or MRI scan, but it provides helpful information about the whole body.

PET scans can sometimes be helpful in finding out if suspicious areas seen on other imaging tests (such as bone scans or CT scans) are tumors. PET scans can also be repeated during treatment to see how well it is working.

Some machines can do a PET and CT scan at the same time (PET/CT scan). This lets the doctor compare areas of higher radioactivity on the PET scan with the more detailed appearance of that area on the CT scan.

Ultrasound

Ultrasound uses sound waves and their echoes to make a picture of internal organs or tumors. For this test, a small, wand-like instrument called a transducer is moved around on the skin (which is first lubricated with gel). It gives off sound waves and picks up the echoes as they bounce off the organs. The echoes are converted by a computer into an image on a screen.

Ultrasound can be used to see if tumors in the pelvis (such as prostate or bladder tumors) are growing or shrinking over time. (This test can’t be used to look at tumors in the chest because the ribs block the sound waves.)

This is an easy test to have, and it uses no radiation.

To learn more about these and other imaging tests, see Imaging (Radiology) Tests.

Biopsy

The results of a physical exam or imaging tests might suggest that someone has RMS (or another type of soft tissue tumor), but a biopsy (removing some of the tumor for viewing under a microscope and other lab testing) is the only way to be certain.

Biopsies can be done in several ways. The approach used depends on where the tumor is, the age of the patient, and the expertise and experience of the doctor doing the biopsy.

Surgical biopsy

The most common biopsy approach is to remove a small piece of tumor during surgery while the patient is under general anesthesia (asleep). In some cases, nearby lymph nodes are also removed to see if the tumor has spread to them. The samples are then sent to a lab and tested.

Needle biopsies

If for some reason a surgical biopsy can’t be done, a less invasive biopsy using a thin, hollow needle may be done. There are 2 kinds of needle biopsies, each of which has pros and cons.

Core needle biopsy: For a core needle biopsy, the doctor inserts a hollow needle into the tumor to withdraw a piece of it (known as a core sample). If the tumor is just under the skin, the doctor can guide the needle into the tumor by touch. But if the tumor is deep inside the body, imaging tests such as ultrasound or CT scans might be needed to help guide the needle into place. The removed core sample is then sent to the lab for testing.

The main advantage of a core needle biopsy is that it does not require surgery, so there is no large incision. Depending on where the tumor is, adults and older children might not need general anesthesia (where they are asleep for the biopsy), but some younger children might. On the other hand, the specimen is smaller than with a surgical biopsy, and if the needle isn’t aimed correctly, it might miss the tumor. If the specimen is not a good sample of the tumor, another biopsy will be needed.

Fine needle aspiration (FNA) biopsy: For this technique, the doctor uses a very thin, hollow needle attached to a syringe to withdraw (aspirate) a small tumor sample. An FNA biopsy is best suited for tumors that can be reached easily (such as those just under the skin), although it can also be used for tumors deeper in the body.

The downside of FNA is that the sample is very small. The pathologist must be experienced with this technique and be able to decide which lab tests will be most helpful on a very small sample. In cancer centers that have the experience to extract the most information from very small amounts of tissue, FNA can be a valuable – though certainly not foolproof – way to diagnose RMS, but it is not usually the preferred biopsy technique.

See Testing Biopsy and Cytology Specimens for Cancer to learn more about different types of biopsies, how the tissue is used in the lab for disease diagnosis, and what the results can tell you.

Bone marrow aspiration and biopsy

These tests are often done after RMS is diagnosed to find out if the cancer has spread to the bone marrow (the soft inner parts of certain bones).

The 2 tests are usually done at the same time. The samples are usually taken from the back of both of the pelvic (hip) bones, but in some patients they may be taken from other bones.

These tests might be done during the surgery to biopsy or remove the main tumor (while the child is still under anesthesia), or they might be done as a separate procedure.

If the bone marrow aspiration is being done as a separate procedure, the patient lies on a table (on their side or belly). After cleaning the skin over the hip, the doctor numbs the area and the surface of the bone with local anesthetic, which can briefly sting or burn. Children may also be given other medicines to help them relax or even go to sleep for the procedure. A thin, hollow needle is then inserted into the bone, and a syringe is used to suck out a small amount of liquid bone marrow.

A bone marrow biopsy is usually done just after the aspiration. Small pieces of bone and marrow are removed with a slightly larger needle that is pushed down into the bone. Once the biopsy is done, pressure will be applied to the site to help stop any bleeding.

The samples of bone and marrow are sent to the lab, where they are looked at and tested for cancer cells.

Lumbar puncture (spinal tap)

This is not a common test for RMS, but it might be done for tumors in the head near the covering of the brain (the meninges). This test is used to look for cancer cells in the cerebrospinal fluid (CSF), which is the liquid that bathes the brain and spinal cord.

For this test, the doctor first numbs an area in the lower part of the back near the spine. The doctor may also recommend that the child be given something to make them sleep so the spinal tap can be done without difficulty or causing harm. A small, hollow needle is then inserted between the bones of the spine to withdraw some of the fluid, which is then sent to the lab for testing.

Lab tests on the biopsy samples

A doctor called a pathologist looks at the biopsy samples under a microscope to see if they contain cancer cells. If cancer is found, the next step is to figure out if it is RMS. In rare cases, the pathologist can see that the cancer cells have small muscle striations, which helps confirm that the cancer is RMS. But most often, other lab tests are needed to be sure.

The pathologist might use special stains on the samples to identify the type of tumor. The stains contain certain proteins (antibodies) that attach to substances in RMS cells but not to other cancers. The stains produce a distinct color that can be seen under a microscope. This lets the pathologist know that the tumor is a rhabdomyosarcoma.

If a diagnosis of RMS is made, the pathologist will also use special lab tests to help determine which kind of RMS it is. This is important because it affects how the cancer is treated. For example, alveolar rhabdomyosarcoma (ARMS), which tends to be more aggressive, typically requires more intense treatment than embryonal rhabdomyosarcoma (ERMS). An important part of this testing is looking for gene or chromosome changes in the cancer cells, such as those discussed in What Causes Rhabdomyosarcoma?

Blood tests

No blood test can be used to diagnose RMS. But certain blood tests may be helpful once a diagnosis has been made.

A complete blood count (CBC) measures the levels of white blood cells, red blood cells, and platelets in the blood. If the CBC result is abnormal at the time of diagnosis it could mean the cancer has spread to the bone marrow, where these blood cells are made. This test can also be used during treatment (such as chemotherapy) to check for possible problems or side effects.

Blood chemistry tests can be used to measure how well the liver and kidneys are working, as well as the levels of certain minerals in the blood.