How Does My Doctor Know I Have Acute Lymphocytic Leukemia?
If your symptoms suggest you may have leukemia, your doctor will first probably check your blood to determine if it has normal numbers of blood cells. People with leukemia often have abnormally high numbers of white blood cells. They may also have immature blood cells, called blasts, normally found only in the bone marrow. If leukemia seems likely, your doctor will perform a bone marrow aspiration and biopsy to determine the type of leukemia you have and your prognosis. A prognosis is a statement about the prospect of surviving and recovering from a disease.
Bone marrow aspiration and biopsy
A doctor performs this test on bones of your hips or, less often, on your sternum, which is your chest bone. Before making a small cut in the skin, the doctor numbs the area with a local anesthetic, which you usually get as an injection. Then the doctor inserts a thin, hollow needle to remove a small amount of liquid bone marrow. You may need to have this done on both hips. Next, the doctor uses a larger needle to remove a solid piece of bone and marrow. Even with anesthesia, you may feel uncomfortable as the doctor removes the marrow and bone. The doctor sends the bone marrow samples to a lab where a specialist, called a pathologist, checks them for leukemia cells. Pathologists may also perform the following tests:
Immunophenotyping. Tests such as immunohistochemistry and flow cytometry can be used for immunophenotyping. These tests require a sample of either your blood or your bone marrow. Immunophenotyping measures the types and amounts of antigens on the surface of leukemia cells. Antigens are substances that cause an immune response. Your doctor uses these facts about your antigens to learn what type of leukemia you have and how the leukemia may grow or spread. Results of this test may take several days.
Cytogenetic analysis. This test requires a sample of either your blood or your bone marrow. The cells are then grown in a laboratory. A pathologist uses a microscope to see the cell's chromosomes, which are pieces of DNA that control cell growth. The DNA changes related to leukemia are not inherited but occur after birth when the cells become leukemia cells. With some types of leukemia, chromosomes may exchange DNA. For example, part of chromosome 1 is on part of chromosome 2 and vice versa. This is called translocation. Another common DNA abnormality is when there may be the wrong number of total chromosomes. A chromosome can be deleted, or one can be added. This information will affect your treatment plan. You will get results from this analysis within a few weeks.
Molecular genetic tests. Other tests may be done on blood or bone marrow samples to look for DNA changes. Fluorescent in situ hybridization ("FISH" for short) is a very sensitive lab test that uses fluorescent dyes to detect some chromosome changes that can't be seen with standard cytogenetic testing. It also provides results within a few days, which is why many centers now use this test. Polymerase chain reaction is another very sensitive DNA test that can find some chromosome changes too small to be seen with a microscope, even if very few leukemia cells are present in a sample.