Chronic lymphocytic leukemia (CLL) is a slow-growing cancer of the blood and bone marrow which produces high levels of abnormal white blood cells (lymphocytes). Unlike normal cells, the abnormal white blood cells in chronic lymphocytic leukemia do not fight infection properly and crowd out red blood cells and platelets, which may result in anemia, infections, and bleeding.
While chronic lymphocytic leukemia starts in the bone marrow, over time the disease spreads through the bloodstream to other parts of the body, especially the lymph nodes, as well as the liver and spleen, which then become enlarged.
There are two main types of chronic lymphocytic leukemia, one that progresses very slowly (B cell), and one that progresses more quickly (T cell), which is the more serious type. Diagnostic tests can determine if chronic lymphocytic leukemia is the type that progresses slowly by finding the proteins, ZAP-70 and CD38, on the leukemia cells, which can predict a better long-term outcome.
Chronic lymphocytic leukemia is the most common type of leukemia in adults, and more often affects individuals who are white, middle-aged, or older, usually over the age of 70, while occurring very rarely in children.
In general, chronic lymphocytic leukemia is categorized as asymptomatic (without symptoms), symptomatic, progressive, refractory (resistant to treatment), or recurrent.
Chronic lymphocytic leukemia is further categorized by the following stages:
Stage 0 – Too many white blood cells (lymphocytes), without any sign or symptom of leukemia. This is a slow-growing stage.
Stage I – Too many white blood cells (lymphocytes) and enlarged lymph nodes.
Stage II – Too many white blood cells (lymphocytes), enlarged liver, spleen, or lymph nodes.
Stage III – Too many white blood cells (lymphocytes), and not enough red blood cells, enlarged liver, spleen, or lymph nodes.
Stage IV – Too many white blood cells, and not enough platelets or red blood cells, enlarged liver, spleen, or lymph nodes.
The stage of chronic lymphocytic leukemia helps to determine the treatment and outcome (prognosis).