Leukemia Diagnosis

  • Diagnosis

    Leukemia is cancer of the blood cells. It begins in the bone marrow when abnormal cells multiply out of control to such an extent that normal blood cells are unable to develop. Leukemia starts in the bone marrow—the soft, spongy material inside bones where blood cells develop from stem cells. Leukemia most often affects the white blood cells, which protect the body against infection. The disease begins when normal development of stem cells into white blood cells goes wrong, creating abnormal white blood cells. Eventually the abnormal white cells overtake other types of blood cells, including red blood cells, which carry oxygen to the body tissues; and platelets, which enable the blood to clot. Leukemia therefore interferes with the blood’s ability to clot and carry oxygen.

    The abnormal white cells may also spread to other parts of the body, including the lymph nodes, skin, spleen, liver, brain, and spinal cord.

    Leukemia is not one disease but a complex group of diseases. There are four main types of leukemia: acute lymphocytic leukemia (ALL), acute myeloid (or myelogenous) leukemia (AML), chronic lymphocytic leukemia (CLL), and chronic myeloid leukemia (CML).

    • Acute lymphocytic leukemia (ALL). ALL develops from white blood cells called lymphocytes. Immature cells that normally grow into lymphoctyes become cancerous and build up rapidly in the bone marrow, replacing normal stem cells. The blood transports these abnormal cells to the lymph nodes, spleen, liver, kidneys, and other organs. These cells can cause meningitis, kidney and liver failure, anemia, and other conditions.
    • Acute myeloid leukemia (AML). AML develops from cells in the bone marrow that normally grow into specific white blood cells called granulocytes. Instead of developing normally, the cells become cancerous and multiply rapidly in the bone marrow. These abnormal cells may grow under the skin, forming small tumors, and result in anemia, meningitis, and damage to the liver, kidneys, and other organs.
    • Chronic lymphocytic leukemia (CLL). In CLL, mature lymphocytes become cancerous and begin to multiply, starting in the lymph nodes. The abnormal cells spread to the bone marrow, and then the spleen and liver, which become enlarged. The shortage of normal blood cells and an abnormal reaction by the immune system causes anemia. The immune system attacks normal tissues, destroys normal red blood cells and platelets, and causes joint inflammation and thyroid gland inflammation (thyroiditis).

      Subtypes of CLL are named according to the type of lymphocyte affected. The most common type of CLL is B-cell leukemia. Less common are T-cell leukemia, Sézary syndrome, and hairy cell leukemia, in which the abnormal cells have hair-like projections when viewed under a microscope.

    • Chronic myeloid leukemia (CML). In CML, bone marrow cells become cancerous and produce large amounts of abnormal granulocytes that may be either immature or mature. These abnormal cells crowd out the normal bone marrow cells. As larger numbers of immature granulocytes enter the bloodstream and bone marrow, the number of red blood cells and platelets decreases.

      Most often, CML progresses to a stage called blast crisis, in which the bone marrow produces only immature granulocytes. This is a sign that the disease has worsened.

    The cause of leukemia is unknown. At present, no one knows what causes leukemia. However, scientists have discovered some risk factors that increase a person’s chance of getting the disease. These may include excess exposure to radiation, or prior treatment for a malignancy, or having had a previous blood disorder. However, most people who develop leukemia do not have any of these risk factors.

    CLL is rare in China and Japan, and remains rare among Japanese people who move to the U.S. This suggests that genetic factors play some role in the development of CLL.

    The symptoms of leukemia, such as frequent infections and easy bruising and bleeding, result from the blood cells’ inability to perform their normal functions. However, at the time of diagnosis of either CLL or CML, patients may have no symptoms. People with leukemia get infections because their white blood cells do not protect them from disease. They become anemic because of a shortage of healthy red blood cells. They bleed and bruise easily because they lack enough platelets to enable their blood to clot.

    Other symptoms depend on which parts of the body the leukemia cells invade. In acute leukemia, cells often collect in the brain and spinal cord, causing headaches, confusion, vomiting, loss of muscle control, and seizures. Some people develop sores on the skin or in the eyes. In both chronic and acute leukemia, various organs may be affected, including the skin, central nervous system, digestive tract, testicles, and kidneys.

    Common symptoms of leukemia include:

    • fever, chills, and other flu-like symptoms
    • fatigue and weakness
    • frequent infections
    • loss of appetite and/or weight
    • swollen or tender lymph nodes, liver, or spleen
    • easy bruising or bleeding
    • swollen or bleeding gums
    • small red spots under the skin
    • sweating, especially at night
    • bone or joint pain

    In acute leukemia, symptoms appear suddenly and worsen rapidly. Symptoms of acute leukemia include:

    • severe infection
    • paleness (a sign of anemia)
    • feeling weak and short of breath
    • nosebleeds
    • easy bruising
    • purple blotches on the skin
    • headaches
    • irritability
    • vomiting
    • joint and bone pain
    • swollen glands
    • swollen, painful, bleeding gums.

    The symptoms of chronic leukemia may take a long time to develop, and may be quite mild at first. Frequently the doctor finds chronic leukemia when you have a blood test during a routine checkup. About a fifth of the people who get chronic leukemia have no symptoms when their cancer is found by a blood test. Often the first symptoms are very general, such as enlarged lymph nodes. You may also lose your appetite, lose weight, feel tired, become short of breath when you exercise, and have a sense of fullness in your abdomen, which is caused by an enlarged spleen.

    As the disease develops, you may grow pale and start to bruise easily. Chronic leukemia usually does not lead to infections until the later stages of the disease. Because CLL progresses slowly, you may not need treatment for years. Treatment is not given until you develop symptoms, or until it is clear that the disease is progressing. In the later stages of CML, you may develop fever, enlargement of the lymph nodes, and lumps under the skin.

    In general, more adults than children get leukemia. Children usually get acute leukemia (particularly ALL), while adults are more likely to have chronic leukemia. The American Cancer Society estimates that every year about 28,800 adults and 2,600 children in the US get leukemia. Most people with chronic leukemia are adults; only about 2% of cases of chronic leukemia occur in children.

    • ALL is the most common cancer in children. Most children who get it are between the ages of 3 and 5, but it can also affect adolescents, and sometimes adults.
    • AML affects mostly adults, but still causes nearly half of the cases of leukemia among children.
    • CLL affects only adults, most of whom are over the age of 60. Men are two to three times more likely to get this form of leukemia than women.
    • CML affects mostly adults. Children get it only rarely.

    Several other factors can increase your risk of getting leukemia.

    • Smoking is a known risk factor for leukemia. Cancer-causing substances in tobacco smoke can travel through the bloodstream and affect other parts of the body, as well as the lungs.
    • High-voltage power lines. Some research suggests that exposure to electromagnetic fields from high-voltage power lines may be a risk factor for leukemia.
    • High-dose radiation. Exposure to high-dose radiation, as from a nuclear reactor accident or from therapeutic radiation, increases the risk for most types of leukemia.
    • Chemicals. Workers exposed to benzene and farm workers exposed to pesticides or herbicides over long periods of time are at greater risk for developing leukemia.
    • Genetic conditions. Certain genetic conditions can increase the risk for leukemia. For example, children with Down syndrome are more likely to get the disease.
    • Chemotherapy. Being treated with certain chemotherapy drugs for other types of cancer increases the risk for AML.
    • A virus known as HTLV-1, which is similar to the virus that causes AIDS, increases a person’s risk for T-cell leukemia.
    • Family history. Having a first-degree relative (parent or sibling) who has had CLL increases a person’s chance for getting CLL.

    To diagnose leukemia, the doctor will first perform a physical exam. Your doctor will ask about your medical history; particularly whether you have any of the general symptoms listed above. In the physical examination, the doctor will feel for swelling of the liver, the spleen, and the lymph nodes in the groin, neck, and underarms. You will also be examined for abnormal bleeding.

    The doctor will then order laboratory and other tests to detect whether you have leukemia, and find out what type it is. Depending on whether you have acute or chronic leukemia, your doctor may conduct one or several tests.

    • Complete blood count (CBC). For this test, a blood sample is examined under the microscope to see how the cells look and to count the numbers of different types of cells. In acute leukemia, there will usually be too many white cells, and most of them will be immature. There will also be too few red cells and platelets. In chronic leukemia, there are also too many white blood cells (although many are mature), and too few red blood cells and platelets.
    • Bone marrow tests. To confirm the diagnosis and to learn what type of leukemia you may have, a sample of bone marrow is examined under a microscope. Bone marrow is obtained either by bone marrow aspiration or biopsy. In a bone marrow aspiration, a doctor inserts a thin needle into a large bone (usually the hip) and draws out a sample of liquid bone marrow. A bone marrow biopsy is done with a larger needle, and extracts a sample of bone as well as bone marrow.
    • Spinal tap. In this test, also called lumbar puncture, the doctor inserts a needle into the space around the spinal cord to draw out fluid, which is then examined to see if it contains leukemia cells. This procedure is done only if a diagnosis of leukemia is made, and is performed to determine if the leukemia cells have spread to other parts of the body.
    • Lymph node biopsy. In a few cases, it may be necessary to remove an entire lymph node to test for leukemia cells.
    • Cytogenetics (chromosome analysis). This test analyzes the shape and number of the chromosomes in the leukemia cells. It can identify chromosome alterations typical of specific types of leukemia.
    • Immunophenotyping. This method uses antibodies that react with substances called antigens on cell membranes. It can distinguish normal cells from leukemic cells, or lymphocytic from myelogenous leukemia cells. It can also identify cell subtypes, which helps your physician decide on the best treatment.
    • Imaging studies. Your doctor may use various methods of creating pictures of the inside of the body to find masses of leukemia cells in different organs.
      • X-rays can reveal a mass in the chest.
      • Ultrasound, which uses sound waves, shows whether the  kidneys, liver, or spleen have been invaded by leukemia cells.
      • Gallium scan or bone scan. For these tests, the doctor injects a radioactive chemical that collects in an area where there is cancer or infection. The location of this area then shows up on an x-ray. These tests can reveal whether bone pain is caused by cancer or infection.

    Since the cause of leukemia is unknown, there is no way to prevent it. You can, however, reduce your risk by not smoking and avoiding exposure to chemicals known to cause leukemia. Since smoking is a known risk factor for AML, avoiding or quitting smoking can reduce your risk for getting that type of leukemia. Avoiding excess exposure to benzene and other cancer-causing chemicals is also advisable.

  • Prevention and Screening

    Since the cause of leukemia is unknown, there is no way to prevent it. You can, however, reduce your risk by not smoking and avoiding exposure to chemicals known to cause leukemia. Since smoking is a known risk factor for AML, avoiding or quitting smoking can reduce your risk for getting that type of leukemia. Avoiding excess exposure to benzene and other cancer-causing chemicals is also advisable.

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