Chronic Lymphocytic Leukemia


When people think of cancer, they often think of a mass or tumor. Blood cancers are different. They begin from cells in the circulatory system and, except for lymphomas, usually do not grow into tumors. Blood cancers, such as chronic lymphocytic leukemia (CLL), may also be called hematologic cancers or malignancies. They include leukemias, lymphomas and multiple myelomas.

Leukemia is a type of blood or hematologic cancer that begins in the blood and bone marrow. It occurs when the bone marrow overproduces excessive immature white blood cells. These immature white cells don’t fight infection like healthy white blood cells do, making an individual susceptible to infection.

CLL is a slow-growing form of leukemia that develops from lymphocytes. Lymphocytes are a type of white blood cell that makes up lymphoid tissue, which is found in the lymph nodes, thymus, spleen, tonsils and other parts of the body (see Figure 1). They are a part of the immune system and develop from lymphoblasts (immature cells found in bone marrow) into mature, infection-fighting cells.

  Figure 1.

CLL develops when immature lymphocytes mutate (change) and multiply uncontrollably. Mutated lymphocytes grow at a faster rate than normal lymphocytes, and they do not die when they should. This leads to an accumulation of abnormal lymphocytes in the blood, which interferes with the normal production of healthy cells. The abnormal lymphocytes do not fight infections like healthy cells and they tend to live longer, which is partly why they build up in the blood or bone marrow. Blood cancers usually do not form solid tumors.

The two main types of lymphocytes that can develop into leukemias are B-lymphocytes (B-cells) and T-lymphocytes (T-cells). B-cells produce protein antibodies that attach to infectious organisms, such as bacteria and viruses, marking them for destruction. T-cells attack infectious organisms directly and play a part in controlling the immune system. CLL starts from B-cells and is, therefore, often called B-cell CLL.

Bone marrow is the soft, spongy center of some bones. Not all bones have bone marrow. The bone marrow is where blood is created and is made up of blood stem cells, more mature blood-forming cells, fat cells and supporting tissues. Blood stem cells can become three main types of cells:

  • Red blood cells carry oxygen from the lungs to other parts of the body.
  • White blood cells fight off infection.
  • Platelets help with clotting to stop bleeding.

Because white blood cells fight off infection, they are part of the immune and lymphatic systems. The immune system is a network of cells, organs and tissues that work together to defend your body against germs and infection (see Figure 2).

                    Figure 2.

The immune system network includes the following:

  • Plasma cells are developed from mature B-cells that respond to infection. Plasma cells make antibodies to help fight germs and infection. Any individual plasma cell makes only one kind of antibody that targets the specific germ for which that plasma cell can attack.
  • Antibodies are proteins created from plasma cells as a reaction to foreign substances, such as bacteria, in the body.
  • Granulocytes are white blood cells containing small granules that help the body fight viruses and bacterial infections.
  • Lymphocytes are cells that make up lymphoid tissue, which is found in the lymph nodes, thymus, spleen, tonsils and other parts of the body. Lymphocytes are a major part of the immune system and develop from lymphoblasts (immature cells found in bone marrow) into mature, infection- fighting cells.
  • Monocytes circulate in the bloodstream and then change and destroy some germs by digesting them.

Although a leukemia diagnosis is overwhelming, all the members of your health care team are working for and supporting you. You are never alone at any point during treatment. Talk with them about all your questions and concerns. The more you know, the more prepared you will be to make decisions about your treatment.

Additional Resources


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