Chronic lymphocytic leukemia overview

Overview
Chronic lymphocytic leukemia (also known as "chronic lymphoid leukemia" or "CLL"), is a type of leukemia, or cancer of the white blood cells (lymphocytes). CLL affects a particular lymphocyte, the B cell, which originates in the bone marrow, develops in the lymph nodes, and normally fights infection. In CLL, the DNA of a B cell is damaged, so that it can't fight infection, but it grows out of control and crowds out the healthy blood cells that can fight infection.

CLL is an abnormal neoplastic proliferation of B cells. The cells accumulate mainly in the bone marrow and blood. CLL is closely related to a disease called small lymphocytic lymphoma (SLL), a type of non-Hodgkin's lymphoma which presents primarily in the lymph nodes. The World Health Organization considers CLL and SLL to be "one disease at different stages, not two separate entities".

In the past, cases with similar microscopic appearance in the blood but with a T cell phenotype were referred to as T-cell CLL. However, it is now recognized that these so-called T-cell CLLs are in fact a separate disease group and are currently classified as T-cell prolymphocytic leukemias.

Acute lymphocytic leukemia (ALL) is a disease of children, but CLL is a disease of adults. Most (>75%) people newly diagnosed with CLL are over age 50, and two-thirds are men. In the United States during 2007, it is estimated there will be 15,340 new cases diagnosed and 4,500 deaths, but because of prolonged survival, many more people are living with CLL.

Most people are diagnosed without symptoms as the result of a routine blood test that returns a high white blood cell count, but as it advances CLL results in swollen lymph nodes, spleen, and liver, and eventually anemia and infections. Early CLL is not treated, and late CLL is treated with chemotherapy and monoclonal antibodies. Survival varies from 5 years to more than 25 years. It is now possible to diagnose patients with short and long survival more precisely by examining the DNA mutations, and patients with slowly-progressing disease can be reassured and may not need any treatment in their lifetimes.

Diagnosis
CLL is usually first suspected by the presence of a lymphocytosis, an increase in one type of the white blood cell, on a complete blood count (CBC) test. This frequently is an incidental finding on a routine physician visit. Most often the lymphocyte count is greater than 4000 cells per mm3 (microliter) of blood but can be much higher.