AML is different from other cancers in that it does not generally grow in one spot to form a tumor. Instead, the abnormal leukemia cells enter from the bone marrow into the bloodstream and spread throughout the body. Because of this, AML has to be classified differently than other types of cancers. Specialists have created an AML classification system based on the different risk factors associated with the disease. The system currently most widely used is the 2016 World Health Organization (WHO) Classification of AML.
As more research on AML emerges, specialists now have more ways of evaluating and categorizing AML. We now know that AML is not a single disease but rather a disease of many types. The different types of AML depend on:
Doctors use genetic testing to evaluate the chromosomes (long strands of DNA) in the leukemia cells. Additional genetic tests also allow doctors to identify specific mutations a patient with AML may have in their leukemia cells. Identifying these changes and abnormalities can help doctors recognize and treat specific subtypes of AML.
Early recognition of these different subtypes can be vital to providing targeted care and therapy.
Mutations, which are genetic changes to specific genes, are found in many cases of AML and can lead to specific types of AML. These mutations allow abnormal cells to grow out of control. The specific type of genetic mutation a patient has can help determine if the AML is more or less aggressive as well as more or less likely to respond to certain treatments.
The most common genes that become mutated in AML include FLT3, IDH1, IDH2, NPM1, DNMT3A, CEBPA, TET2, and KIT. Drugs have been and are currently being developed to target these specific genetic mutations. This personalized medicine approach allows for the treatment of AML to be much more effective for many patients.
Four types of chromosomal changes can take place in AML. These changes help determine a patient's prognosis and what type of treatment should be given. Understanding what these chromosomal abnormalities mean and what their shorthands are can be vital in finding the right treatment:
APL is the most common subtype of AML, and it is correlated with a more favorable prognosis. APL has a very specific treatment of vitamin therapy that is often effective. The mutation associated with APL is called a translocation, or a swapping of genes between two chromosomes, specifically between chromosomes 15 and 17. The shorthand for this mutation is t(15;17). “t” stands for translocation and (15;17) represents which chromosomes are being swapped. There are 23 pairs of chromosomes numbered 1-23 in human cells. See our APL page for more specific information.
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