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Chronic Lymphocytic Leukemia (CLL): Introduction 

What is cancer?

Cancer is when cells in the body change and grow out of control. Your body is made up of tiny building blocks called cells. Normal cells grow when your body needs them, and die when your body does not need them any longer. Cancer is made up of abnormal cells that grow even though your body doesn’t need them. In most types of cancer, the abnormal cells grow to form a lump or mass called a tumor.

What is leukemia?

Leukemia is different from most other types of cancer. Leukemia is cancer that starts in the bone marrow. This is where new blood cells are made. Leukemia cells are early forms of blood cells, most often white blood cells. When a person has leukemia, the body makes too many abnormal blood cells. Leukemia cells do not usually form tumors, but they can travel with the blood all over the body. That means leukemia can affect organs all over the body.                                                   

Two types of white blood cells can turn into leukemia:

  • Lymphoid cells (lymphocytes). This is called lymphocytic leukemia.

  • Myeloid cells (myelocytes). This is called myeloid or myelogenous leukemia.

Leukemia can also be either acute or chronic. Acute leukemia tends to grow very quickly and needs to be treated right away. Chronic leukemia often grows more slowly.

What is chronic lymphocytic leukemia (CLL)?

Chronic lymphocytic leukemia (CLL) is a type of leukemia that starts in the lymphoid cells in the bone marrow. These are cells that normally help the body fight infection. As the leukemia cells grow, they can crowd out the normal cells in the bone marrow. This can lead to not enough of different types of blood cells. People with CLL have too many lymphocytes in their blood, but these cells are not normal and don't help fight infection. In fact, people with CLL are more likely to get an infection. 

CLL is a type of chronic leukemia. This means it tends to grow slowly. Many people with CLL do not have any symptoms when it’s first found. This kind of leukemia often doesn’t need to be treated right away. But some cases of CLL grow faster than others. Healthcare providers look at the cells in a lab to see what kind of CLL a person has.                                                                                                                                                                                   

Talk with your healthcare provider

If you have questions about CLL, talk with your healthcare provider. Your healthcare provider can help you understand more about this type of leukemia.

Online Medical Reviewer: Cunningham, Louise, RN
Online Medical Reviewer: LoCicero, Richard, MD
Date Last Reviewed: 6/1/2018
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