Tests for Ewing Sarcoma

An x-ray is often the first test done if a bone tumor is suspected. Doctors can usually spot a bone tumor like Ewing sarcoma on an x-ray, but other imaging tests and a biopsy are often needed to tell for sure.

X-rays can also be used to see whether a cancer has spread to the lungs. It can find larger tumors, but it is not as good as a CT scan for spotting smaller tumors. If a CT scan of the chest is done, an x-ray may not be needed.

MRIs 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 see details better.

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

MRIs also can show the bone marrow as well as the soft tissues around the tumor, including nearby blood vessels and nerves. Knowing the extent of the tumor is very important when planning surgery or radiation therapy.

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

MRI scans usually show better details than a CT scan (described below).

A CT scan combines many x-ray pictures to make detailed cross-sectional images of the inside of the body. A contrast material may be injected into a vein before the scan to help see details better.

CT chest scans are often used to see whether Ewing sarcoma 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.

CT scans can also be used to guide a biopsy needle into a tumor (a CT-guided needle biopsy). For this test, you are on the CT scanning table while the doctor guides a biopsy needle into the tumor. CT scans are repeated until the needle is within the tumor and a piece can be removed for testing.

For a PET scan, a form of radioactive sugar called FDG is injected into the blood. The amount of radioactivity used is very low and will pass out of the body in a day or so. Because cancer cells in the body are growing quickly, they absorb large amounts of sugar.

About an hour after getting the FDG injection, you are moved to a table in the PET scanner and lie down for about 30 minutes while a special camera creates 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 helpful in showing whether Ewing sarcoma has spread and finding out whether abnormal areas seen on other imaging tests (such as a CT scan) 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 appearance of that area on the CT scan.

A bone scan can show whether a cancer has spread to other bones, and may be part of the workup for people with bone cancers. This test is useful because it can show the entire skeleton at once. A positron emission tomography (PET) scan, described above, can often provide similar information, so a bone scan might not be needed if a PET scan is done.

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 that can detect radioactivity creates a picture of the skeleton.

Areas of active bone changes attract the radioactivity and appear as “hot spots” on the skeleton. Hot spots may suggest areas of cancer, but other bone diseases can also cause the same pattern. To make an accurate diagnosis, other tests such as plain x-rays, MRI scans, or even a biopsy might be needed. The amount of radioactivity used in this test is very low, and the material passes out of the body within a day or so.

For a surgical biopsy, a doctor (typically an orthopedic surgeon) removes a piece of the tumor through a cut made in the skin. If only a piece of it is removed, it is called an incisional biopsy. If the entire tumor is removed (not just a small piece), it's called an excisional biopsy.

These biopsies are often done in an operating room with the patient under general anesthesia (in a deep sleep). They can also be done using a nerve block, which numbs a large area of the body.

For a core needle biopsy, a thin, hollow needle is inserted through the skin and into the tumor to remove a small sample. The biopsy can be done with numbing medicine injected into the skin and other tissues over the biopsy site. In this case, you are awake for the procedure but should feel little or no pain. In some cases, you might need sedation or general anesthesia.

Often, the doctor can aim the needle by feeling the suspicious area if it's near the surface of the body. If the tumor can’t be felt because it's too deep, the doctor can guide the needle into the tumor using an imaging test such as an ultrasound or CT scan. These types of image-guided biopsies are usually done by a doctor who is an interventional radiologist.

For this test, a portion of the biopsy sample is treated with special proteins (antibodies) that attach to substances found on Ewing sarcoma cells. Chemicals (stains) are then added so that cells containing these substances change color and can be seen under a microscope. This tells the pathologist more about the cells and can help them diagnose Ewing sarcoma.

Some substances found on Ewing sarcoma cells can be found on other types of cells, so a few different proteins may need to be used to know that the tumor is Ewing sarcoma.

These tests look at the chromosomes (long strands of DNA) inside the cells. Normal human cells have 23 pairs of chromosomes, 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, 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: For this test, cancer cells are grown in a lab dish and the chromosomes are looked at under a microscope. Doctors look at the number and structure of the chromosomes to find any changes.

Cytogenetic testing usually takes a few weeks because the cancer cells take time to grow before the chromosomes are ready to be looked at.

Not all chromosome changes can be seen under a microscope. Other lab tests can often help find these changes.

Fluorescent in situ hybridization (FISH): This is another way to look at chromosomes and genes. It uses special dyes that only attach to specific parts of certain chromosomes. FISH can find most chromosome changes (such as translocations) that are visible under a microscope in standard cytogenetic tests, as well as some changes too small to be seen with routine cytogenetic testing.

FISH can be used to look for specific changes in chromosomes. It is very accurate and can usually provide results within a couple of days.

Polymerase chain reaction (PCR): PCR is a very sensitive test that can find chromosome and gene changes too small to be seen under a microscope, even if there are only a few tumor cells in the sample.

Next-generation sequencing (NGS): This test may also be used to look for gene changes in cancer cells that might not be seen on routine cytogenetic tests. NGS can sometimes tell doctors more about the best treatments and prognosis (outlook).