This is a medical question of type : exams and tests 
 How to diagnose Ewing Sarcoma ? 
 Tests that examine the bone and soft tissue are used to diagnose and stage Ewing sarcoma.
                    Procedures that make pictures of the bones and soft tissues and nearby areas help diagnose Ewing sarcoma and show how far the cancer has spread. The process used to find out if cancer cells have spread within and around the bones and soft tissues is called staging.   In order to plan treatment, it is important to know if the cancer is in the area where it first formed or if it has spread to other parts of the body. Tests and procedures to detect, diagnose, and stage Ewing sarcoma are usually done at the same time.   The following tests and procedures may be used to diagnose or stage Ewing sarcoma:         -   Physical exam and history : An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patients health habits and past illnesses and treatments will also be taken.    -   MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body, such as the area where the tumor formed. This procedure is also called nuclear magnetic resonance imaging (NMRI).    -   CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, such as the area where the tumor formed or the chest, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.    -   PET scan (positron emission tomography scan): A procedure to find malignant tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Malignant tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do. A PET scan and a CT scan are often done at the same time. If there is any cancer, this increases the chance that it will be found.    -   Bone scan : A procedure to check if there are rapidly dividing cells, such as cancer cells, in the bone. A very small amount of radioactive material is injected into a vein and travels through the bloodstream. The radioactive material collects in the bones with cancer and is detected by a scanner.    -   Bone marrow aspiration and biopsy : The removal of bone marrow and a small piece of bone by inserting a hollow needle into the hipbone. Samples are removed from both hipbones. A pathologist views the bone marrow and bone under a microscope to see if the cancer has spread.    -  X-ray: An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body, such as the chest or the area where the tumor formed.    -   Complete blood count (CBC): A procedure in which a sample of blood is drawn and checked for the following:               - The number of red blood cells, white blood cells, and platelets.      - The amount of hemoglobin (the protein that carries oxygen) in the red blood cells.      - The portion of the blood sample made up of red blood cells.              -   Blood chemistry studies : A procedure in which a blood sample is checked to measure the amounts of certain substances, such as lactate dehydrogenase (LDH), released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease.
                
                
                    A biopsy is done to diagnose Ewing sarcoma.
                    Tissue samples are removed during a biopsy so they can be viewed under a microscope by a pathologist to check for signs of cancer. It is helpful if the biopsy is done at the same center where treatment will be given.         -   Needle biopsy : For a needle biopsy, tissue is removed using a needle. This type of needle biopsy may be done if its possible to remove tissue samples large enough to be used for testing.    -   Incisional biopsy : For an incisional biopsy, a sample of tissue is removed through an incision in the skin.     -   Excisional biopsy : The removal of an entire lump or area of tissue that doesnt look normal.        The specialists (pathologist, radiation oncologist, and surgeon) who will treat the patient usually work together to decide where the needle should be placed or the biopsy incision should be made. This is done so that the biopsy doesn't affect later treatment such as surgery to remove the tumor or radiation therapy.   If there is a chance that the cancer has spread to nearby lymph nodes, one or more lymph nodes may be removed and checked for signs of cancer.   The following tests may be done on the tissue that is removed:         -   Cytogenetic analysis : A laboratory test in which cells in a sample of tissue are viewed under a microscope to look for certain changes in the chromosomes.    -   Immunohistochemistry : A test that uses antibodies to check for certain antigens in a sample of tissue. The antibody is usually linked to a radioactive substance or a dye that causes the tissue to light up under a microscope. This type of test may be used to tell the difference between different types of cancer.    -   Flow cytometry : A laboratory test that measures the number of cells in a sample, the percentage of live cells in a sample, and certain characteristics of cells, such as size, shape, and the presence of tumor markers on the cell surface. The cells are stained with a light-sensitive dye, placed in a fluid, and passed in a stream before a laser or other type of light. The measurements are based on how the light-sensitive dye reacts to the light.