What is Chronic Lymphocytic Leukemia (CLL)?

Leukemia is cancer that forms in your bone marrow, the soft, spongy tissue inside your bones where blood cells are produced. Your bone marrow contains immature, blood-forming stem cells that eventually develop into mature red blood cells, white blood cells, and platelets. In Chronic Lymphocytic Leukemia (CLL), the bone marrow produces too many malignant white blood cells. CLL is "chronic" because it is slow-growing and not very aggressive. "Lymphocytic" refers to the type of white blood cell (lymphocytes) affected. Lymphocytes are a type of white blood cell that helps your body fight off infection. The abnormal lymphocytes of CLL do not fight infection and can also crowd out your healthy blood cells causing conditions like anemia (low red blood cells) and thrombocytopenia (low platelets). CLL is classified into subtypes based on the type of lymphocyte affected: B lymphocytes or T lymphocytes. B-cell CLL is more common.

CLL is the most common form of leukemia, with over 20,000 new cases a year, mostly in older adults. CLL usually progresses slowly compared to other forms of leukemia; however, the abnormal cells can eventually build up in your body and invade your blood, lymph nodes, and other organs like the liver and spleen. Still, some people with the disease don't experience symptoms for years.