What is leukemia? Leukemia is a cancer that begins in the soft, inner part of the bones (bone marrow), and in most cases moves into the blood. It can spread to other parts of the body including the lymph nodes, liver, spleen, central nervous system and testes. “Chronic leukemia” refers to the slow progression of the disease, which when combined with little or no symptoms can cause the leukemia to go undetected until the advanced stages of the disease. What is chronic lymphocytic leukemia (CLL)? Chronic lymphocytic leukemia (CLL) is one of four main types of leukemia. CLL begins with a change to a single white blood cell, or lymphocyte, of the bone marrow. Over time, the CLL cells multiply, replacing normal lymphocytes in the marrow and lymph nodes. As the amount of lymphocytes increases in the blood and bone marrow, there is less room for healthy white and red blood cells as well as platelets, which may result in infection, anemia and bleeding.