What is Adult Acute Myeloid Leukemia (AML) ?

What is Adult Acute Myeloid Leukemia (AML) ?
What is leukaemia?
Leukaemia is a cancer of cells in the bone marrow (the cells which develop into blood cells).

Cancer is a disease of the cells in the body. There are many types of cancer which arise from different types of cell. What all cancers have in common is that the cancer cells are abnormal and do not respond to normal control mechanisms. Large numbers of cancer cells build up because they multiply out of control, or because they live much longer than normal cells, or both.

With leukaemia, the cancerous cells in the bone marrow spill out into the bloodstream. There are several types of leukaemia. Most types arise from cells which normally develop into white blood cells. (The word leukaemia comes from a Greek word which means white blood.) If you develop leukaemia it is important to know exactly what type it is. This is because the outlook (prognosis) and treatments vary for the different types. Before discussing the different types of leukaemia it may help to know some basics about normal blood cells and how they are made.

What is Adult acute myeloid leukemia (AML) ?
Adult acute myeloid leukemia (AML) is a cancer of the blood and bone marrow. This type of cancer usually gets worse quickly if it is not treated. It is the most common type of acute leukemia in adults. AML is also called acute myelogenous leukemia, acute myeloblastic leukemia, acute granulocytic leukemia, and acute nonlymphocytic leukemia.

What causes acute myeloid leukaemia (AML)?
A leukaemia is thought to start first from one abnormal cell. What seems to happen is that certain vital genes, which control how cells divide, multiply and die, are damaged or altered. This makes the cell abnormal. If the abnormal cell survives it may multiply out of control and develop into a leukaemia.

In most cases of AML, the reason why an immature white blood cell becomes abnormal is not known. There are certain risk factors which increase the chance that leukaemia will develop, but these only account for a small number of cases. Risk factors known for AML include:
  • High-dose radiation (for example, previous radiotherapy for another condition).
  • Exposure to the chemical benzene (this is in cigarettes).
  • Some genetic conditions which can increase the risk of having AML in the future. The most common is Down's syndrome.
  • AML is not an inherited condition and does not run in families.

What are signs and symptoms of Adult acute myeloid leukemia (AML)?
Signs and symptoms of adult AML include fever, feeling tired, and easy bruising or bleeding.

The early signs and symptoms of AML may be like those caused by the flu or other common diseases. Check with your doctor if you have any of the following:
  • Fever.
  • Shortness of breath.
  • Easy bruising or bleeding.
  • Petechiae (flat, pinpoint spots under the skin caused by bleeding).
  • Weakness or feeling tired.
  • Weight loss or loss of appetite.

How is acute myeloid leukaemia (AML) diagnosed and assessed?

1. A blood test
A blood test can often suggest the diagnosis of AML. The test will typically show a low number of: red blood cells, normal white blood cells and platelets. Some blast cells which have spilled into the bloodstream from the marrow are also usually seen. Sometimes large numbers of blast cells occur in the bloodstream. Further tests are usually done to confirm the diagnosis.

2. A bone marrow sample
For this test a small amount of bone marrow is removed by inserting a needle into the pelvic bone (or sometimes the breastbone (sternum)). Local anaesthetic is used to numb the area. Sometimes a small core of marrow will also be taken (a trephine biopsy). The samples are put under the microscope to look for abnormal cells and also tested in other ways. This can confirm the diagnosis. See separate leaflet called Bone Marrow Biopsy and Aspiration for more details.

3. Cell and chromosome analysis
Detailed tests are done on abnormal blast cells obtained from the bone marrow sample or blood test. The chromosomes within the cells are checked for certain changes. Chromosomes are the parts in the cell which contain DNA - the genetic make-up of the cell. Various subtypes of AML can be diagnosed by detecting changes which occur to parts of one or more chromosome. (These chromosome changes only occur in the leukaemia cells, not the normal body cells.) It is important to know the exact subtype of AML, as the treatments and outlook (prognosis) can vary depending on the type.

4. Various other tests
A lumbar puncture is done if symptoms suggest that the abnormal cells have spread to the brain or spinal cord. This test collects a small amount of fluid from around the spinal cord - cerebrospinal fluid (CSF). It is done by inserting a needle between the vertebrae in the lower (lumbar) region of the back. The fluid is examined for leukaemia cells. A chest X-ray, blood tests, and other tests are done to assess your general well-being.

Tests that examine the blood and bone marrow are used to detect (find) and diagnose adult AML.

The following tests and procedures may be used:

1. 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.

2. 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 sample made up of red blood cells.
  • Peripheral blood smear : A procedure in which a sample of blood is checked for blast cells, the number and kinds of white blood cells, the number of platelets, and changes in the shape of blood cells.

3. Bone marrow aspiration and biopsy 
The removal of bone marrow, blood, and a small piece of bone by inserting a hollow needle into the hipbone or breastbone. A pathologist views the bone marrow, blood, and bone under a microscope to look for signs of cancer.

4. 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. Other tests, such as fluorescence in situ hybridization (FISH), may also be done to look for certain changes in the chromosomes.

5. Immunophenotyping 
A process used to identify cells, based on the types of antigens or markers on the surface of the cell. This process is used to diagnose the subtype of AML by comparing the cancer cells to normal cells of the immune system. For example, a cytochemistry study may test the cells in a sample of tissue using chemicals (dyes) to look for certain changes in the sample. A chemical may cause a color change in one type of leukemia cell but not in another type of leukemia cell.

6. Reverse transcription–polymerase chain reaction test (RT–PCR)
A laboratory test in which cells in a sample of tissue are studied using chemicals to look for certain changes in the structure or function of genes. This test is used to diagnose certain types of AML including acute promyelocytic leukemia (APL).
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