Ewing's Sarcoma
Diagnosis

In addition to a complete medical history and physical examination of your child, diagnostic procedures for Ewing sarcoma will include an X-ray examination of the painful area. There may be multiple diagnostic tests such as:

  • Bone scans — A nuclear imaging method to detect bone diseases and tumors and determine the cause of bone pain or inflammation.
  • Computed tomography (CT or CAT) scan — With the help of computers, X-rays produce images of thin cross sections of the body to provide more detail than conventional X-rays. CT scans often are used to supplement other diagnostic X-rays. The CT scan of the chest is essential to look for any cancer that may have spread to the lungs.
  • Magnetic resonance imaging (MRI) — Magnetic resonance imaging (MRI) uses magnets, rather than X-rays, to produce detailed images of the body. The MRI machine sends radio waves into the body and then measures the response with a computer to produce an image or picture. MRIs are used for certain types of tumors because they can produce a better image than X-rays.
  • Blood tests — A complete blood count (CBC) will show abnormalities in the blood. An abnormal CBC result might suggest the spread of cancer to the bone marrow. A blood test for levels of an enzyme called lactate dehydrogenase (LDH) should be obtained. Elevation of the serum LDH level at diagnosis is associated with Ewing's sarcoma and other cancers. The red blood cell sedimentation rate also may be elevated in Ewing's sarcoma.
  • Biopsy — Although the results of imaging studies may strongly suggest that cancer is present, a biopsy or tissue test is the only way to be certain. A biopsy is also the only way to distinguish a Ewing's sarcoma from other types of cancer. If the tumor involves bone, a doctor experienced in the treatment of Ewing's sarcoma should perform a biopsy. Proper planning of the biopsy location and technique can prevent later complications and reduce the amount of surgery during treatment.

Biopsies

There are several ways to obtain a sample of the tumor for diagnosis. If the tumor is small and in a good location, the surgeon can completely remove it while your child is under general anesthesia. This is often called an excisional biopsy.

If the tumor is large or cannot be removed without risk to adjacent vital tissue, part of the tumor is removed in an incisional biopsy.

A small sample also can be taken by a needle biopsy, which involves placing a needle through the skin into the tumor. This technique usually isn't used for bone tumors.

If your child is going to have surgery, you may be asked to allow the surgeon to obtain extra tissue for additional studies. No matter what method is used, tissue will be sent to a pathologist, a doctor specializing in diagnosing diseases by laboratory tests.

If your child is going to have general anesthesia for the bone biopsy, the surgeon also may plan other procedures while your child is asleep, to avoid performing more operations than necessary. For example, if your child is thought to have cancer in the chest or elsewhere, the surgeon may want to obtain a biopsy sample of these suspected lumps while your child is still asleep. The pediatric hematologist (blood specialist) and oncologist (cancer specialist) also may perform bone marrow biopsies to determine if the cancer has spread.

At the time of the bone biopsy, a pathologist may examine the tissue under the microscope to determine if it is cancer while your child is still asleep. If it is Ewing's sarcoma, the surgeon can place a central venous access catheter for cancer treatment, an intravenous tube, into the blood vessel of your child's chest during the same operation.

If a biopsy indicates Ewing's sarcoma, additional studies may be performed since Ewing's sarcoma shares some of the same characteristics of other childhood cancers.

  • Immunohistochemistry — A portion of the sample is treated with special laboratory antibodies to identify substances that are found in Ewing's sarcoma cells, but not in other types of cancer. Additional chemicals or stains are added so cells containing these substances change color and can be easily recognized under a microscope.
  • Cytogenetics — Close examination of chromosomes from Ewing's sarcoma cells usually reveals translocations, which means that part of one chromosome breaks off and attaches to another chromosome. Ewing's sarcoma cells have translocations involving chromosomes 11 and 22 as well as chromosomes 21 and 22. These characteristics can help distinguish Ewing's sarcoma from other types of cancer.
  • Reverse transcription polymerase chain reaction (RTPCR) — This test is another way to recognize translocations in Ewing's sarcoma cells. Instead of using a microscope to look for the chromosomal changes as in cytogenetic testing, RTPCR relies on chemical analysis of the RNA, a substance related to DNA, from genes affected by the translocation. RTPCR testing is more sensitive than cytogenetics in detecting translocations in Ewing's sarcoma cells. It can be used to confirm the type of tumor and may prove useful in monitoring for residual or recurrent cancer after treatment.
  • Bone Marrow Aspiration and Biopsy — Cells are removed from bone marrow, the spongy network of tissues inside the bones, to check for signs of cancer. Depending upon the diagnosis, this procedure may be done periodically throughout your child's treatment to determine whether cancerous cells have spread to the bone marrow. A bone marrow aspiration and biopsy usually takes 15 to 20 minutes to complete.

Bone Marrow Aspiration and Biopsy

Understandably, bone marrow aspirations may be frightening to you and your child. A local quick-acting anesthetic is injected deep under the skin to numb the puncture site and help control pain. Whenever possible, we give you the option of having the procedure performed under general anesthesia. In the aspiration, a sample of the liquid part of bone marrow is removed.

Immediately following a bone marrow aspiration, your child also may undergo a bone marrow biopsy to remove a small core of bone marrow. This procedure may be necessary to confirm the presence of cancer since the liquid may not contain enough cells.

A bone marrow biopsy usually is performed at the same site as the aspirate. Although the biopsy needle may look frightening, only a very small sample of the spongy bone marrow is removed, using a procedure similar to bone marrow aspiration. The difference is that a side-to-side motion of the needle is used to take out a small sample of the spongy marrow, which is the most painful part of the procedure.

Staging of Ewing's Sarcoma

There are two primary stages of Ewing's sarcoma:

  • Localized tumor — A localized tumor is confined to the tissue where it developed and may also include nearby tissues, such as muscle or tendons. An Ewing's sarcoma is considered localized only after appropriate imaging studies, such as X-rays, CT and MRI scans, and the bone marrow biopsy and aspirate do not detect distant spread to other organs. Even when imaging studies do not show metastases, most patients are assumed to have micrometastases or small areas of cancer that have spread and can be found only by examining tissue samples under the microscope.
  • Metastatic tumor — A metastatic tumor has spread from its original location to other parts of the body, such as the lungs or to other bones and bone marrow not directly connected to the bone where the tumor started. Less common sites of Ewing's sarcoma metastases include the liver and lymph nodes.

Reviewed by health care specialists at UCSF Benioff Children's Hospital.

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