Diagnostic tests are used to detect (find) and diagnose childhood soft tissue sarcoma. The following tests and procedures may be used:         -   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.    -   X-rays : An x-ray is a type of energy beam that can go through the body onto film, making pictures of areas inside the body.     -   MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas of the body, such as the chest, abdomen, arms, or legs. 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 chest or abdomen, 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.    -   Ultrasound exam: A procedure in which high-energy sound waves (ultrasound) are bounced off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram. The picture can be printed to be looked at later.
                         - If tests show there may be a soft tissue sarcoma, a biopsy is done. One of the following types of biopsies is usually used:          -   Core needle biopsy : The removal of tissue using a wide needle. This procedure may be guided using ultrasound, CT scan, or MRI.     -   Incisional biopsy : The removal of part of a lump or a sample of tissue.     -   Excisional biopsy : The removal of an entire lump or area of tissue that doesnt look normal. A pathologist views the tissue under a microscope to look for cancer cells. An excisional biopsy may be used to completely remove smaller tumors that are near the surface of the skin. This type of biopsy is rarely used because cancer cells may remain after the biopsy. If cancer cells remain, the cancer may come back or it may spread to other parts of the body.  An MRI of the tumor is done before the excisional biopsy. This is done to show where the original tumor is and may be used to guide future surgery or radiation therapy.        The placement of needles or incisions for the biopsy can affect the success of later surgery to remove the tumor. If possible, the surgeon who will remove any tumor that is found should be involved in planning the biopsy.    In order to plan the best treatment, the sample of tissue removed during the biopsy must be large enough to find out the type of soft tissue sarcoma and do other laboratory tests. Tissue samples will be taken from the primary tumor, lymph nodes, and other areas that may have cancer cells. A pathologist views the tissue under a microscope to look for cancer cells and to find out the type and grade of the tumor. The grade of a tumor depends on how abnormal the cancer cells look under a microscope and how quickly the cells are dividing. High-grade and mid-grade tumors usually grow and spread more quickly than low-grade tumors.    Because soft tissue sarcoma can be hard to diagnose, the tissue sample should be checked by a pathologist who has experience in diagnosing soft tissue sarcoma.   One or more of the following laboratory tests may be done to study the tissue samples:         -   Molecular test : A laboratory test to check for certain genes, proteins, or other molecules in a sample of tissue, blood, or other body fluid. A molecular test may be done with other procedures, such as biopsies, to help diagnose some types of cancer. Molecular tests check for certain gene or chromosome changes that occur in some soft tissue sarcomas.    -   Reverse transcriptionpolymerase chain reaction (RTPCR) test: A laboratory test in which cells in a sample of tissue are studied using chemicals to look for changes in the expression of certain genes. When genes are expressed they make specific proteins that are needed for the structure, function, and monitoring of the bodys tissues and organs. This test is done in order to identify the type of tumor.     -   Cytogenetic analysis : A laboratory test in which cells in a sample of bone marrow, blood, amniotic fluid, tumor or other tissue is viewed under a microscope to look for changes in the chromosomes. Fluorescence in situ hybridization (FISH) is a type of cytogenetic analysis.    -   Immunocytochemistry : A test that uses antibodies to check for certain antigens (markers) in a sample of cells. The antibody is usually linked to an enzyme or fluorescent dye that causes the cells that have that marker to become visible under a microscope. This type of test may be used to tell the difference between different types of soft tissue sarcoma.