How is rhabdomyosarcoma diagnosed?
Certain signs and symptoms might suggest that a person may have rhabdomyosarcoma (RMS), but tests are typically needed to confirm the diagnosis.
Signs and symptoms of rhabdomyosarcoma
The symptoms of RMS depend largely on where the tumor is:
- When the tumor is in the trunk, limbs, or groin (including the testicles), the first sign is usually a mass or swelling. Most often it doesn't cause any pain or other problems, but it may in some cases.
- Tumors around the eye can cause the eye to bulge or the child to appear to be cross-eyed.
- Tumors in the ear or nasal sinuses can cause an earache, headache, or sinus congestion.
- Tumors in the bladder or prostate may lead to blood in the urine, while a tumor in the vagina may lead to vaginal bleeding. Any of these tumors may grow big enough to make it hard or painful to urinate or have bowel movements.
- Tumors in the abdomen or pelvis can cause vomiting, abdominal pain, or constipation.
- RMS rarely develops in the bile ducts (small tubes leading from the liver to the intestines), but when it does it can cause yellowing of the eyes or skin.
One or more of these symptoms usually leads parents to bring a child to the doctor. Less often, the child may have symptoms related to more advanced RMS, such as bone pain, constant cough, weakness, or weight loss.
Keep in mind that many of these signs and symptoms are more likely to be caused by something other than RMS. Still, if your child has any of these symptoms, check with your doctor so that the cause can be found and treated, if needed.
Medical history and physical exam
If your child has any signs or symptoms that may suggest RMS, the doctor will want to get a complete medical history to learn about any symptoms and how long your child has had them. The doctor will also examine your child to look for possible signs of RMS or other health problems. For example, the doctor may be able to see or feel an abnormal mass in the body.
If symptoms or the results of the physical exam suggest your child might have RMS, other tests will need to be done. These might include imaging tests, biopsies, and/or lab tests.
Imaging tests use x-rays, magnetic fields, radioactive substances, or sound waves to create pictures of the inside of the body. Imaging tests may be done for a number of reasons, including:
- To help find out whether a suspicious area might be cancerous
- To determine the extent of a tumor or learn how far a cancer may have spread
- To help determine if treatment is working
Patients who have or may have RMS will get one or more of these tests.
These are sometimes used to look for tumors, but their use is limited mainly to looking at bones because they do not show much detail in internal organs. An x-ray of the chest 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 or CAT) scan
The CT scan is an x-ray test that produces detailed cross-sectional images of parts of the body, including soft tissues such as muscles. Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around your child while he or she lies on a table. A computer then combines these pictures into images of slices of the part of the body being studied.
This test can provide fairly detailed information about a tumor, including how large it is and if it has invaded 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.
Before the scan, your child may be asked to drink a contrast solution and/or get an intravenous (IV) injection of a contrast dye that helps better outline abnormal areas in the body. Your child may need an IV line through which the contrast dye is injected. The contrast may cause some flushing (a feeling of warmth, especially in the face). Some people are allergic and get hives. Rarely, more serious reactions like trouble breathing or low blood pressure can occur. Be sure to tell the doctor if your child has any allergies or has ever had a reaction to any contrast material used for x-rays.
CT scans take longer than regular x-rays. During the test, the table slides in and out of the scanner, a ring-shaped machine that completely surrounds the table. Your child will need to lie still on a table while this is being done. Younger children may be given medicine to help keep them calm or even asleep during the test. Many medical centers now use spiral CT (also known as helical CT), which completes the scan more quickly. It also yields more detailed pictures and lowers the dose of radiation received during the test.
Magnetic resonance imaging (MRI) scan
Like CT scans, MRI scans give detailed images of soft tissues in the body. But MRI scans use radio waves and strong magnets instead of x-rays. The energy from the radio waves is absorbed and then released in a pattern formed by the type of body tissue and by certain diseases. A computer translates the pattern into a very detailed image of parts of the body. A contrast material called gadolinium may be injected into a vein before the scan to better show details. The contrast material usually does not cause allergic reactions.
This test may 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, as they provide a detailed view of the muscle, fat, and connective tissue around the tumor. This is important when planning surgery or radiation therapy. MRI is also very useful if your child's doctor is concerned about possible spread to the spinal cord or brain.
MRI scans take longer than CT scans, often up to an hour. Your child may have to lie inside a narrow tube, which is confining and can be distressing. Newer, more open MRI machines can help with this, but the test still requires staying still for long periods of time. The MRI machine also makes loud buzzing and clicking noises that may be disturbing. Sometimes, younger children are given medicine to help keep them calm or even asleep during the test.
A bone scan can help show if a cancer has spread to the bones, and is often part of the workup for children with RMS. 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 a vein (IV). The substance settles in areas of damaged bone throughout the entire skeleton over the course of a couple of hours. Your child then lies on a table for about 30 minutes while a special camera detects the radioactivity and creates a picture of the skeleton. Younger children may be given medicine to help keep them calm or even asleep 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 in an area, but other bone diseases can also cause the same pattern, so other imaging tests such as plain x-rays or MRI scans, or even a bone biopsy might be needed.
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. The amount of radioactivity used is very low. Because cancer cells in the body are growing quickly, they absorb large amounts of the radioactive sugar.
After about an hour, your child will lie on a table in the PET scanner for about 30 minutes while a special camera creates a picture of areas of radioactivity in the body. The picture is not finely detailed like a CT or MRI scan, but it provides helpful information about the whole body.
PET scans are not used routinely to help diagnose RMS, but they can sometimes be very 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 monitor the cancer over time.
Some newer machines are able to do a PET and CT scan at the same time (PET/CT scan). This allows the doctor to compare areas of higher radioactivity on the PET scan with the more detailed appearance of that area on the CT.
Ultrasound uses sound waves and their echoes to make a picture of internal organs or tumors. For this test, a small, microphone-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 that is displayed on a computer 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 done, and it uses no radiation. Your child simply lies on a table, and a technician moves the transducer over the part of the body being looked at.
The results of imaging tests may strongly suggest that someone has RMS, but a biopsy (removing some of the tumor for viewing under a microscope and other lab testing) is the only way to be certain. Usually several different kinds of lab tests are done on the sample to sort out what kind of tumor it is.
Biopsies can be done in several ways. The approach that is used will depend on where the mass is located, the age of the patient, and the expertise and experience of the doctor doing the biopsy.
The most common biopsy approach is to surgically remove a small piece of tumor while the patient is under general anesthesia (asleep) and have it looked at by a pathologist (a doctor who diagnoses diseases from the results of lab tests). In some cases, nearby lymph nodes may also be removed and tested to see if the tumor has spread.
If for some reason a surgical biopsy cannot be done, a less invasive biopsy using a hollow needle may be used. 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 tissue (core sample). If the tumor is near the surface of the body, the doctor can guide the needle into the tumor by touch. But if the tumor is deep within the body, imaging tests such as ultrasound or CT scans may be needed to guide the needle into place. The core sample that is removed is then used in lab tests to help make the diagnosis.
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 may not need general anesthesia (where they are asleep for the biopsy), but some children may still need it. On the other hand, the specimen is smaller than with a surgical biopsy, and if it is not aimed correctly, the needle may miss the cancer. If the specimen is not a good sample of the tumor, another biopsy will be needed.
Fine needle aspiration (FNA) biopsy: This technique uses a very small hollow needle attached to a syringe to withdraw (aspirate) a small tumor sample. An FNA biopsy is ideally suited to tumors near the surface of the body that can be reached easily.
The downside of FNA is that the sample is very, 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 – diagnostic approach, but it is not usually the preferred biopsy technique.
Bone marrow aspiration and biopsy
These tests aren't used to diagnose RMS, but they may be done after the diagnosis to find out if the tumor has spread to the bone marrow. 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 the sternum (breastbone) or other bones.
These tests may be done during the surgery to treat the main tumor (while the child is still under anesthesia), or they may be done as a separate procedure.
If the bone marrow aspiration is being done as a separate procedure, the child lies on a table (on his or her 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 may cause a brief stinging or burning sensation. Even with the local anesthetic, most patients still have some brief pain when the marrow is removed. In most cases, the child is also given other medicines to reduce pain or even be asleep during 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. A small piece of bone and marrow is removed with a slightly larger needle that is twisted as it is pushed down into the bone. The biopsy may also cause some brief pain. Once the biopsy is done, pressure will be applied to the site to help stop any bleeding.
Lumbar puncture (spinal tap)
Lumbar puncture is not a common test for RMS, but it may 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 him or her sleep so the spinal tap can be done without difficulty or causing harm. A small, hollow needle is then placed between the bones of the spine to withdraw some of the fluid.
Lab tests on the biopsy samples
A pathologist will look at the biopsy samples under a microscope to try to determine if they contain cancer cells. If the pathologist finds cancer, the next step is to figure out if the cancer is RMS. In rare cases, the pathologist can see that the cancer cells have small muscle striations (myofibrils), which confirm that the cancer is RMS. But in most cases, other lab tests are needed to confirm the diagnosis.
Pathologists may use special stains on the samples to identify the type of tumor. The stains contain special proteins (antibodies) that specifically attach to substances in RMS cells but not 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.
Sometimes the tumor will also be tested for gene abnormalities. Genetic tests look for chromosome translocations and other DNA changes such as those discussed in the section "Do we know what causes rhabdomyosarcoma?"
If a diagnosis of RMS is made, the pathologist will also use these tests to help determine which kind of RMS your child has. This is important because it affects how the child is treated. For example, alveolar rhabdomyosarcoma (ARMS), which tends to be more aggressive, typically requires more intensive treatment than embryonal rhabdomyosarcoma (ERMS).
Last Medical Review: 04/26/2012
Last Revised: 04/26/2012