Cancer is a disease in which cells grow in an abnormal way. They are supposed to divide in a controlled way to replace old or damaged cells. With leukemia, blood cells grow and divide quickly, making more than are needed.
Normal Blood Cells and the Development of Leukemia
All blood cells start in the bone marrow as stem cells. Stem cells mature into many types of blood cell that have certain roles in the body. These are:
- Red blood cells—Carry oxygen from the lungs to the organs and cells of the body.
- Platelets—Fix broken blood vessels by making the blood clot to stop bleeding.
- White blood cells—Helps the body fight infection and disease.
New, healthy cells are made in the bone marrow. This keeps the number of blood cells in a healthy range. With leukemia, too many abnormal cells are made and they crowd out the bone marrow. This makes it hard for new, healthy cells to be made. Cancer moves around the body in the blood and lymph streams. This keeps organs like the spleen, liver, brain, and lymph nodes from working as they should.
Types of Leukemia
Leukemia is grouped by how fast it grows and the type of blood cell affected. The groups are:
- Acute—Cells are not fully formed. They grow and spread quickly. The effects on the body happen fast.
- Chronic—Cells are mature and fully formed, meaning they look like normal cells. However, they do not work like they should. Chronic leukemia may not be noticed until symptoms appear. This can take years. In some people, it is found during a routine blood test.
Leukemia is also grouped by the bone marrow cells it starts in:
- Myeloid—Affects myeloid cells which grow into certain types of white blood cells, red blood cells, and platelets.
- Lymphocytic or lymphoblastic—Affects lymphoid cells that normally grow into a type of white blood cell called a lymphocyte.
Common types of leukemia include:
- Acute lymphoblastic leukemia (ALL)—Most common type of leukemia in young children, but it can happen in older adults.
- Acute myeloid leukemia (AML)—Found in both adults and children.
- Chronic lymphocytic leukemia (CLL)— Most common in older adults. It can happen in younger adults and in children, but this is rare.
- Chronic myeloid leukemia (CML)—Found mainly in adults, but also in a very small number of children.
Revision Information
- Reviewer: EBSCO Medical Review Board Mohei Abouzied, MD, FACP
- Review Date: 12/2018 -
- Update Date: 03/14/2019 -