Tests that examine the blood and bone marrow are used to detect (find) and diagnose childhood ALL. The following tests and procedures may be used to diagnose childhood ALL and find out if leukemia cells have spread to other parts of the body such as the brain or testicles:         -   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 patient's health habits and past illnesses and treatments will also be taken.    -   Complete blood count (CBC) with differential : A procedure in which a sample of blood is drawn and checked for the following:               - The number of red blood cells and platelets.      - The number and type of white blood cells.      - The amount of hemoglobin (the protein that carries oxygen) in the red blood cells.      - The portion of the 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 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.    -   Bone marrow aspiration and biopsy : The removal of bone marrow and a small piece of bone by inserting a hollow needle into the hipbone or breastbone. A pathologist views the bone marrow and bone under a microscope to look for signs of cancer. The following tests are done on blood or the bone marrow tissue that is removed:               -  Cytogenetic analysis : A laboratory test in which the cells in a sample of blood or bone marrow are viewed under a microscope to look for certain changes in the chromosomes of lymphocytes. For example, in Philadelphia chromosome positive ALL, part of one chromosome switches places with part of another chromosome. This is called the Philadelphia chromosome.       -  Immunophenotyping : A laboratory test in which the antigens or markers on the surface of a blood or bone marrow cell are checked to see if they are lymphocytes or myeloid cells. If the cells are malignant lymphocytes (cancer) they are checked to see if they are B lymphocytes or T lymphocytes.             -   Lumbar puncture : A procedure used to collect a sample of cerebrospinal fluid (CSF) from the spinal column. This is done by placing a needle between two bones in the spine and into the CSF around the spinal cord and removing a sample of the fluid. The sample of CSF is checked under a microscope for signs that leukemia cells have spread to the brain and spinal cord. This procedure is also called an LP or spinal tap. This procedure is done after leukemia is diagnosed to find out if leukemia cells have spread to the brain and spinal cord. Intrathecal chemotherapy is given after the sample of fluid is removed to treat any leukemia cells that may have spread to the brain and spinal cord.     -   Chest x-ray : An x-ray of the organs and bones inside the chest. 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. The chest x-ray is done to see if leukemia cells have formed a mass in the middle of the chest.