Leukemia cells are abnormal, immature cells that form in the bone marrow. There are two main types of these cells: lymphoid cells and myeloid cells. The four most common types of leukemia are classified, in part, based on whether the abnormal cells involved are lymphoid cells or myeloid cells.
What Are Leukemia Cells?Leukemia cells are abnormal, immature cells produced by blood-forming tissue (such as bone marrow). These cells are named based on the cells that they affect -- lymphoid or myeloid cells. Each of these types of leukemia cells will be discussed in this article.
Understanding Normal Blood Cells and Leukemia CellsBefore talking about leukemia cells, it may be helpful to understand normal blood cells and how they form. Blood cells form in the bone marrow, which is the soft material in the center of most bones. Normally, the bone marrow begins by producing immature blood cells, called stem cells and blasts. As these blood cells mature, they form into one of three types of mature blood cells:
- Red blood cells that carry oxygen and other materials to all tissues of the body
- White blood cells that fight infection and disease.
- Platelets that help prevent bleeding by causing blood clots to form.
Mature blood cells are created from one of two types of stem cells -- lymphoid stem cells or myeloid stem cells. As lymphoid stem cells mature, they become lymphoid blasts (also known as lymphoblasts), then lymphocytes, and finally white blood cells. As myeloid stem cells mature, they become myeloid blasts (also known as myeloblasts), then myelocytes (also called granulocytes), and finally either white blood cells, red blood cells, or platelets (depending on the type of granulocyte).
In people with leukemia, the bone marrow produces abnormal cells -- either abnormal lymphoid cells or myeloid cells. When abnormal lymphoid cells are created, it is known as lymphocytic leukemia (or lymphoblastic leukemia). When abnormal myeloid cells are created, it is known as myeloid leukemia (or myelogenous leukemia).
There are four common types of leukemia based on the cells formed, along with the aggressiveness of the cancer. These types include:
- Chronic lymphocytic leukemia (CLL)
- Chronic myelogenous leukemia (CML)
- Acute lymphocytic leukemia (ALL)
- Acute myeloid leukemia (AML).