What are the different types of AML? There are many types of AML and a growing number based on our increasing understanding of the biology of the disease. Over a number of years, we classified AML almost simply by how it looked under the microscope. And we were able to identify very early immature AML types versus slightly more mature types. And we got about seven or eight different subtypes that we would commonly recognize that way. Over the years, we have added to our understanding by looking at some of the standard genetic changes that drive a lot of different types of AML. And so we have further subcategorized AML based on genetic changes. And that gives us many more subtypes. More recently, we've complemented those genetic changes with molecular tests. And the molecular tests are more sensitive and they look at very specific pathways that may be dysregulated and that thus drive the leukemia. And so the molecular tests complement the genetic information and together give us many more subtypes of AML. What are the most common types of AML? This is an interesting, interesting evolution that we've gone through. Back in 1976, a group of pathologists from the US, from Britain, and from France got together and formed the FAB classification system. And this was based solely upon how the cells looked under the microscope. So we would say this is myeloblastic leukemia with differentiation. This was acute promyelocytic leukemia, monocytic leukemia, but all based on how the cells looked. And then around 2008, the World Health Organization came up with a new classification system based upon the genetic abnormalities that occur. So now patients who have certain chromosome abnormalities or even now gene mutations in a newer version of this classification system are considered to have different types of leukemia. So the disease is now named upon the chromosomal and genetic abnormalities that the disease has as opposed to how it looks under the microscope. And this is really a more accurate way to prognosticate, and it can be important for deciding what the best therapy is for patients as well. How do genetic subtypes work in AML? Initially, this new classification system focused on certain chromosomal abnormalities. So there were patients who had recurrent translocations where a piece of chromosome 8 and 21 changed place, or there was an inversion in chromosome 16, or missing parts of chromosomes, deletions of chromosomes 5 and 7, extra chromosomes. And each one of these became a subtype. And then as we learn more, there can be additional gene mutations, point mutations in a whole variety of genes. And so now there's probably around 20 different types. I haven't counted recently, but the number keeps growing as we learn more about the biology of leukemia and recognize that each one of these genetic abnormalities and chromosome abnormalities behaves in its own unique way. And sometimes it gets treated in a unique way. It becomes a new type of leukemia. So it's a constantly evolving process.
HealthTree • November 30, 2022
