Diagnosing Acute Myeloid Leukemia (AML)
To diagnose leukemia, doctors perform a number of tests. Usually, doctors begin with a blood test (called a CBC, or complete blood count). Although the blood test may show leukemia cells, doctors need to examine a sample of bone marrow before confirming the exact diagnosis. This sample is obtained by performing a bone marrow aspirate, where doctors take a small amount of fluid from the bone marrow, where blood cells are made. Then they examine the fluid under a microscope to confirm the type of cancer before they begin treatment.
An additional test that may be performed along with the bone marrow aspirate is a bone marrow biopsy. A bone marrow biopsy may help in making a diagnosis when there are too few cells in the aspirate sample.
A spinal tap is usually performed to look for leukemia in the central nervous system. Following these tests, your doctor will ask the laboratory to perform cytogenetic tests (tests that check the leukemia’s chromosomes for mistakes, also called mutations). Not all chromosome mutations are easily found and sometimes they can only be seen using powerful laboratory techniques called molecular analysis (tests that look inside the chromosomes for extremely tiny mistakes). These tiny molecular mutations of the chromosomes may have a powerful impact upon the ability to be cured and have recently become the target of new medical treatments of leukemia. Based upon the chromosomal findings, your doctor can diagnosis the subtype of AML and can make an initial prognosis (prediction) for the chances of remission and long-term cure.
Types of AML
AML can be divided into different subtypes which help your doctor determine both the general prognosis for cure as well as the best type of treatment.
AML is caused by mutations in myeloid white blood cells. The body copies new white and red blood cells millions of times per day. In a normal person, a new blood cell (called a “blast”) will gradually develop (or “differentiate”) into a mature blood cell. In a cancer patient, a mutation during replication causes the blood cells to “freeze” in an early stage of development. For AML to develop, this mutation has to be combined with another mutation that disrupts how cells replicate, causing these immature blasts to multiply. There are several types of abnormalities in chromosomes that cause normal myeloid cells to become leukemia cells.
Recent advances have allowed doctors to pinpoint some of the specific mutations that cause different sub-types of AML. We now know that some of these mutations are low risk, and can be more easily cured. Other mutations are high risk, meaning these sub-types of AML have higher rates of relapse and higher risk of treatment failure.