 Welcome back. Today we're going to discuss leukemias. The first step in understanding leukemias is understanding the whole process going on with the blood cells. So let's take a look at this chart to start. So we have a multi-potential hemopoietic stem cell up here at the top and that can differentiate into several different types of cells. It can become a myeloid progenitor cell or it can break into a lymphoid progenitor cell. The lymphoid progenitor cells will become your Bs and T lymphocytes eventually. Your myeloid progenitor cells can differentiate into an extended list of options including your megakaryocytes that eventually become your platelets. It can also differentiate into your red blood cells and then you also have your granulocytes and your monocytes with your basophils, etocinophils, neutrophils, and then your monocytes that become macrophages. So looking at the leukemias, a leukemia is a cancer of the blood-forming tissues including the bone marrow. Most of the time we see cancer signs developing in the bone marrow first before we see them elsewhere in the body. Let's look and see what kind of symptoms we can see. Typically, you're going to find weight loss, fever, and frequent infections as your most common symptoms for leukemia. Also, as we looked earlier just a minute ago, we can also see an anemia because that original cell that creates the erythrocytes can be cut off and we have a low red blood cell number. We also can commonly see some infections as we see here. That's because we're not going to have the white blood cells that respond and fight off infections as we normally do. Another common symptom that we see down here on the bottom right is easily bleeding and bruising. This can also lead to hemorrhage and all of this is due to the decreased platelets. So there are several different types of leukemias that are out there. We're going to talk about five specific today. The lymphoid neoplasms, which we talked about, is the ones that differentiate into your B and T cells. We have the acute lymphoblastic leukemia, also known as ALL. We have the chronic lymphocytic leukemia, also known as CLL, and you have your hairy cell leukemia. On the myeloid side of things, we have two different types of leukemia. You have the acute myelogenous leukemia, also known as AML, and our chronic myelogenous leukemia, also known as CML. When you look at a blood smear for a normal individual that does not have leukemia, on the left side you'll see a large number of your erythrocytes, or your red blood cells, all throughout. And then you'll have a good amount of platelets that you can see here in blue. And then we also will have several white blood cells. You'll have your lymphocytes and your neutrophils and your monocytes. All of these cells will be present under normal conditions with normal blood counts. But when you have leukemias, you're going to have quite a few changes in your blood counts. First of all, as you can see on the right side, there's quite a few less red blood cells than there are on the left. That's because those red blood cells are not having the opportunity to differentiate into mature red blood cells because of the leukemia in another part of that progeny list. You will also see that there are less platelets in the right side. You'll also find quite a few extra cells here in the purple, these lymphocytes. So this is an example of a lymphocytic leukemia because we have an increased number of lymphocytes that we don't normally have.