Tests for Rhabdomyosarcoma

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

A chest x-ray can be done to look for cancer that might have spread to the lungs, although it is often not needed if a chest CT scan is being done. CT scans create more detailed pictures than x-rays.

Ultrasound uses sound waves and their echoes to look inside the body. For this test, a small, wand-like instrument called a transducer is moved around on the skin. It gives off sound waves and picks up the echoes as they bounce off the organs. The echoes are made into an image on a computer screen. The test uses no radiation and does not cause any pain.

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 cannot be used to look at tumors in the chest well because the ribs block the sound waves.

The CT scan combines many x-ray pictures to make detailed cross-sectional images of the inside 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.

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

This test can be used instead of a CT scan to look at the tumor and the tissues around it. MRI is very 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 location and size 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 tumors spreading to the spinal cord or brain.

For a PET scan, a radioactive substance (usually a type of sugar 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 done again 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 image of that area on the CT scan.

Being still during this test is important. Younger children may be given medicine to help them stay calm or even sleep during the test.

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, called technetium-99, is injected into the blood and travels to the bones. A special camera can detect this material, and it creates a picture of the skeleton. Being still during this test is important. Younger children may be given medicine to help them stay calm or even sleep during the test.

Areas of active bone changes attract the radioactivity and show up as “hot spots” on the scan. These areas may suggest cancer, but other bone diseases can also cause the same pattern, so other tests like plain x-rays or MRI scans, or even a bone biopsy might be needed. The amount of radioactivity used is very low and will pass out of the body within a day or so.

A bone scan might not be needed if a PET scan is done, as the PET scan can often provide similar information.

The most common biopsy approach is to remove a piece of the tumor through a cut made in the skin. The patient is under general anesthesia (asleep) during the surgery. 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.

In some cases, 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 remove 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. 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 a 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 younger children might. On the other hand, the specimen is smaller than with a surgical biopsy, and if the needle is not aimed correctly, it might not get the best sample. 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 used 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.

Compared to other biopsy methods, FNA samples are 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 used 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.

RMS can spread to the bone marrow (the soft inner parts of certain bones). To check if cancer cells are in the bones, bone marrow aspiration and biopsy tests are done.

These 2 tests are usually done at the same time. The samples are usually taken from 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.

After cleaning the skin over the hip bone, the doctor numbs the area and the surface of the bone with local anesthetic, which can briefly sting or burn. Children may be given other medicines to help them relax or even go to sleep for the procedure if being done separately from the tumor surgery.

During the bone marrow aspiration, a thin, hollow needle is inserted into the bone, and a syringe is used to suck out a small amount of liquid bone marrow.

During the bone marrow biopsy small pieces of bone and marrow are removed by inserting a larger needle. 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.

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

It is important for the child to be still for the procedure. The doctor may do the test at the same time as other tests where the child will be under general anesthesia (asleep). If the test is done by itself, the doctor may recommend that the child be given something to make them sleep so the spinal tap can be done without difficulty or causing harm. Some older children may be able to have the test done while awake.

After cleaning the skin, the doctor will numb an area in the lower part of the back near the spine. A small, hollow needle is inserted between the bones of the spine to remove some of the fluid, which is then sent to the lab for testing.