Tests for Ewing Tumors

Ewing tumors (Ewing sarcomas) are usually found because of signs or symptoms a person is having. If the doctor suspects a tumor, exams and tests will be needed to find out for sure.

If a Ewing tumor is found, other tests will then be needed to learn more about it.

Medical history and physical exam

If a person has signs or symptoms that could be from a bone or soft tissue tumor, the doctor will want to get a complete medical history to find out more about the symptoms and how long they have been present.

The doctor will also do a physical exam, paying special attention to any areas causing pain or swelling.

If the doctor suspects a bone tumor (or another type of tumor), more tests will be done. These might include imaging tests, biopsies, and/or lab tests.

Imaging tests

Imaging tests (such as x-rays, MRI scans, CT scans, bone scans, and PET scans) create pictures of the inside of the body. Imaging tests might be done for many 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 may have spread
• To help determine if treatment is working

People who have or might have a Ewing tumor will get one or more of these tests.

X-rays

If a lump in or near a bone doesn’t go away or if the doctor suspects a bone tumor for some other reason, an x-ray of the area will probably be the first test done. Doctors can usually spot a bone tumor on an x-ray and can often tell if it is likely to be a Ewing tumor. But other imaging tests might be needed as well.

Even if an x-ray image strongly suggests a Ewing tumor, a biopsy (described below) will still be needed to confirm that it is cancer rather than some other problem, such as an infection.

Magnetic resonance imaging (MRI) scan

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

An MRI is often done to get a better look at an abnormal area seen on an x-ray. An MRI usually can show if it is likely to be a tumor, an infection, or some type of bone damage from another cause.

MRIs can also help determine the extent of a tumor, as they show the marrow inside bones as well as the muscle, fat, and connective tissue around the tumor. Knowing the extent of the tumor is very important when planning surgery or radiation therapy.

MRI scans might also be done to see if the cancer has spread to other areas, such as the spine or pelvis (hip area).

Computed tomography (CT) scan

A 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.

CT scans of the chest are often used to see if a Ewing tumor has spread to the lungs. MRI scans are usually a bit better at showing the extent of the main tumor itself, but a CT scan of the tumor may be done as well.

Bone scan

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

Areas of active bone changes attract the radioactivity and appear as “hot spots” on the skeleton. These areas may suggest the presence of cancer, but other bone diseases can also cause the same pattern. To be sure, other tests such as plain x-rays or MRI scans, or even a bone biopsy, might be needed.

A bone scan can help show if a cancer has spread to bones in other parts of the body, so it might be part of the workup for a Ewing tumor. This test is useful because it can show the entire skeleton at once. (A positron emission tomography [PET] scan can often provide similar information, so a bone scan might not be needed if a PET scan is done.)

Positron emission tomography (PET) scan

For a PET scan, a form of radioactive sugar (known as FDG) is injected into the blood. Because cancer cells are growing quickly, they 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 be very helpful in showing the spread of Ewing tumors and in finding out whether abnormal areas seen on other imaging tests (such as a CT scan) are tumors. PET scans can also be repeated during treatment to see how well it is working.

Many 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.

Biopsy of the tumor

The results of imaging tests might strongly suggest a person has a Ewing tumor (or some other type of cancer), but a biopsy (removing some of the tumor for viewing with a microscope and other lab testing) is the only way to be certain.

If the tumor is in a bone, it is very important that the biopsy is done by an orthopedic surgeon experienced in treating bone tumors. Whenever possible, the biopsy and the surgery to treat the cancer should be planned together, and the same surgeon should do both. Careful planning of the biopsy can help prevent later complications and might reduce the amount of surgery needed later on.

There are a few ways to get a sample of the tumor to diagnose Ewing tumors.

Incisional biopsy

For most suspected Ewing tumors, an incisional biopsy (taking out only a piece of the tumor) is done. This can be done in a couple of ways:

• Surgical (open) biopsy: The surgeon cuts away a piece of the tumor through an opening on the skin.
• Needle (closed) biopsy: The surgeon puts a large, hollow needle through the skin and into the tumor to remove a piece of it.

Incisional biopsies are often done while the patient is under general anesthesia (in a deep sleep), but in older teens and adults they are sometimes done with just sedation and a local anesthetic (numbing medicine).

Excisional biopsy

In very rare cases, if the tumor is small enough and in a good location, the surgeon can completely remove it while the patient is under general anesthesia (asleep). This is called an excisional biopsy.

Other procedures that might be done during the biopsy

If general anesthesia is going to be used for the biopsy, the surgeon may also plan other procedures while the patient is asleep to avoid having to do them as separate operations later on. For example, if the tumor is thought to have spread to the chest or elsewhere, the surgeon may take biopsy samples of these suspected tumors during the surgery. The doctor might also do a bone marrow biopsy (see below) at this time to see if the cancer has spread to the bone marrow.

During the biopsy (while the patient is still asleep), the biopsy samples can be checked quickly under a microscope for cancer. If it looks like a Ewing tumor, the patient will very likely need chemotherapy as part of treatment, so the surgeon may place a small flexible tube, known as a central venous catheter, into a large vein in the chest area during the same operation. The catheter end lies just under or outside on the skin. It can stay in place for several months during treatment. The catheter gives doctors and nurses easier access to the vein, so not as many needle sticks are needed to give chemo or do blood draws later.

Bone marrow aspiration and biopsy

These tests are used to see if the cancer cells have spread into the bone marrow, the soft inner parts of certain bones. The tests might be done once a Ewing tumor has been diagnosed because it is important to know if the tumor has spread to the bone marrow.

Bone marrow aspiration and biopsy are usually done at the same time. In most cases the marrow samples are taken from the back of the pelvic (hip) bones. These tests may be done during surgery to biopsy or treat the main tumor (while the patient 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 patient lies on a table (on their side or belly). The area over the hip is cleaned, and the skin and the surface of the bone are numbed with a local anesthetic, which may cause a brief stinging or burning sensation. Children may also be given other medicines to make them sleepy, or they might 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 pushed down into the bone. Once the biopsy is done, pressure is applied to the site to help stop any bleeding.

Samples from the bone marrow are sent to a pathology lab, where they are looked at and tested for cancer cells.

Testing biopsy samples

A doctor called a pathologist looks at all biopsy specimens under a microscope to see if they contain cancer cells. If cancer is found, the specific type of cancer can often be determined as well. But because cells from Ewing tumors share many of the same features as cells from other types of cancer, more lab tests are often needed.

Immunohistochemistry

For this test, a portion of the biopsy sample is treated with special proteins (antibodies) that attach to substances found on Ewing tumor cells but not on other cancers. Chemicals (stains) are then added so that cells containing these substances change color and can be seen under a microscope. This lets the pathologist know that the cells are from a Ewing tumor.

Chromosome tests

Normal human cells have 23 pairs of chromosomes (strands of DNA), each of which is a certain size and looks a certain way under the microscope. Ewing tumor cells almost always have chromosome translocations, where 2 chromosomes swap pieces of their DNA. In most cases, the cells have translocations between chromosomes 22 and 11. Less often, the translocation is between other chromosomes. Finding these changes can help doctors tell Ewing tumors from other types of cancer. Other types of chromosome changes can also be found in some Ewing tumors.

Cytogenetics: In this lab test, the cells are looked at with a microscope to see if the chromosomes have any abnormalities. A drawback of this test is that it usually takes about 2 to 3 weeks because the cells must grow in lab dishes for a couple of weeks before their chromosomes are ready to be looked at with a microscope. 

Fluorescent in situ hybridization (FISH): This test looks more closely at tumor cell DNA using special fluorescent dyes that only attach to specific genes or parts of chromosomes. FISH can find most chromosome changes (such as translocations) that can be seen in standard cytogenetic tests, as well as some gene changes too small to be seen with cytogenetic testing. FISH is very accurate and can usually provide results within a couple of days.

Polymerase chain reaction (PCR): PCR is a very sensitive test that is often able to detect very small numbers of cells with translocations, which wouldn’t be detected by cytogenetics.

PCR is also useful in looking for cancer that remains or comes back after treatment. For example, if PCR testing of a bone marrow sample after treatment finds cells with a typical Ewing tumor translocation, it’s likely that at least some cancer remains, and that more treatment is needed.

Genomics testing: Some newer lab tests can look at all of the genes inside cancer cells at the same time. These tests, also known as next generation sequencing, can sometimes help guide treatment of the cancer.

Blood tests

No blood test can be used to diagnose Ewing tumors. 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. An abnormal CBC result (that is, low blood cell counts) might suggest the cancer has spread to the bone marrow, where these blood cells are made.

A blood test for levels of an enzyme called lactate dehydrogenase (LDH) is typically done at diagnosis. A high LDH level is often a sign that there is more cancer in the body.

Standard blood tests are done often to check a patient’s general health both before treatment (especially before surgery) and during treatment (such as chemotherapy) to look for possible problems or side effects. These tests often include a CBC to check blood cell levels and blood chemistry tests to measure how well the liver and kidneys are working.