NCCN Guidelines for Patients® | Chronic Lymphocytic Leukemia

10 NCCN Guidelines for Patients ® : Chronic Lymphocytic Leukemia, 2018 1 Chronic lymphocytic leukemia CLL basics Illustration Copyright © 2017 Nucleus Medical Media, All rights reserved. Figure 3 Genetic material in cells Most human cells contain the “blueprint of life”—the plan by which our bodies are made and work. The plan is found inside of chromosomes, which are long strands of DNA that are tightly wrapped around proteins. Genes are small pieces of DNA that contain instructions for building new cells and controlling how cells behave. Humans have about 24,000 genes. Inside of cells are coded instructions for building new cells and controlling how cells behave. These instructions are called genes. Genes are a part of DNA ( d eoxyribo n ucleic a cid), which is grouped together into bundles called chromosomes. See Figure 3. Changes (mutations) in genes cause normal B-cells to become cancer cells. Researchers are still trying to learn what causes genes to change and cause cancer. Changes in genes cause cancer cells to grow more quickly and live longer than normal cells. Normal cells grow and then divide to form new cells when needed. They also die when old or damaged as shown in Figure 4. In contrast, cancer cells make new cells that aren’t needed and don’t die quickly when old or damaged. CLL can be a fast- or slow-growing cancer. Often, it grows slowly. If slow, you may not know you have CLL for years because you have no symptoms. Over time, CLL cells will crowd out healthy cells in bone marrow. A normal number of red blood cells and platelets will not be made. As a result, you may feel tired, lose weight, and get sick easily. CLL may also spread to your lymph nodes, liver, and spleen, and cause these organs to enlarge.