Rhabdomyosarcoma - Childhood: Diagnosis

Approved by the Cancer.Net Editorial Board, 06/2021

ON THIS PAGE: You will find a list of common tests, procedures, and scans that doctors use to find the cause of the medical problem. Use the menu to see other pages.

Doctors use many tests to find, or diagnose, cancer. They also do tests to learn if cancer has spread to another part of the body from where it started. If this happens, it is called metastasis. For example, imaging tests can show if the cancer has spread. Imaging tests show pictures of the inside of the body. Doctors may also do tests to learn which treatments could work best.

For most types of cancer, a biopsy is the only sure way for the doctor to know if an area of the body has cancer. In a biopsy, the doctor takes a small sample of tissue for testing in a laboratory. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis.

How rhabdomyosarcoma is diagnosed

There are many tests used for diagnosing rhabdomyosarcoma. Not all tests described here will be used for every person. Your child’s doctor may consider these factors when choosing a diagnostic test:

  • The type of cancer suspected

  • Your child’s signs and symptoms

  • Your child’s age and general health

  • The results of earlier medical tests

In addition to a physical examination, the following tests may be used to diagnose rhabdomyosarcoma:

  • Biopsy. A biopsy is the removal of a small amount of tissue for examination under a microscope. Other tests can suggest that cancer is present, but only a biopsy can make a definite diagnosis. The type of biopsy performed will depend on the location of the cancer. If the tumor is near the surface of the body, the child will be given a local anesthetic to numb the area during the procedure. If it is deeper inside the body, a general anesthetic (medication to block the awareness of pain) will be used. A pathologist then analyzes the sample(s). A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease.

  • Immunocytochemistry tests. These are special stains done on the cells taken during the biopsy to help the doctor make an accurate diagnosis of rhabdomyosarcoma. Stains that show muscle cell development, including actin, desmin, MyoD-1, and Myogenin, are most helpful.

  • Genetic tests of tumor tissue. Chromosomes are structures that contain the genes in a cell. Changes in certain chromosomes in the tumor cells, called chromosomal translocations, can help doctors identify the alveolar subtype of rhabdomyosarcoma (see Introduction), although some alveolar rhabdomyosarcomas lack any specific translocation. Doctors will do a genetic test of the tumor tissue, usually a test called fluorescence in-situ hybridization (FISH test), to see if translocations have occurred.

  • Bone marrow biopsy. The doctor may also perform a bone marrow biopsy. Rhabdomyosarcoma can spread to the bone marrow, and only a biopsy can find it there. A bone marrow biopsy is the removal of a small amount of tissue using a special needle. The sample(s) are then analyzed by a pathologist. A common site for a bone marrow biopsy is the pelvic bone, which is located in the lower back by the hip. Doctors generally give a type of medication called "anesthesia" beforehand to numb the area. Anesthesia is medication that blocks the awareness of pain. Stronger types of anesthesia can also be used to lessen the pain.

Imaging tests

To determine where the cancer is located and if it has spread, the doctor may use the following imaging tests:

  • X-ray. An x-ray is a way to create a picture of the structures inside of the body using a small amount of radiation.

  • Computed tomography (CT or CAT) scan. A CT scan takes pictures of the inside of the body using x-rays taken from different angles. A computer combines these pictures into a detailed, 3-dimensional (3D) image that shows any abnormalities or tumors. A CT scan can be used to measure the tumor’s size. Sometimes, a special dye called a contrast medium is given before the scan to provide better detail of the image. This dye can be injected into a patient’s vein or given as liquid to swallow.

  • Magnetic resonance imaging (MRI). An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. MRI can be used to measure the tumor’s size. A special dye called a contrast medium is given before the scan to create a clearer picture. This dye can be injected into a patient’s vein or given as a liquid to swallow.

  • Bone scan. A bone scan uses a radioactive tracer to look at the inside of the bones. The amount of radiation in the tracer is too low to be harmful. The tracer is injected into a patient’s vein. It collects in areas of the bone and is detected by a special camera. Healthy bone appears lighter to the camera, and areas of injury, such as those caused by cancer, stand out on the image.

  • Positron emission tomography (PET) or PET-CT scan. A PET scan is usually combined with a CT scan (see above), called a PET-CT scan. However, you may hear your doctor refer to this procedure just as a PET scan. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive substance is injected into a patient’s body. This substance is absorbed mainly by organs and tissues that use the most energy. Because cancer tends to use energy actively, it absorbs more of the radioactive substance. However, the amount of radiation in the substance is too low to be harmful. A scanner then detects this substance to produce images.

After these diagnostic tests are done, your child’s doctor will review the results with you. If the diagnosis is cancer, these results will also help the doctor describe the cancer. This is called staging.

The next section in this guide is Stages and Groups. It explains the system doctors use to describe the extent of the disease. Use the menu to choose a different section to read in this guide.