Chronic lymphocytic leukemia (CLL) is a mature B cell neoplasm characterized by a progressive accumulation of monoclonal B lуmрhοсуteѕ. It is the same disease as small lymphocytic lymphoma (SLL), which is diagnosed when the monoclonal lymphocytes accumulate in lymph nodes.

CLL/SLL is the most common leukemia in North America and is mainly a disease of older adults (median age at diagnosis is ~70).

Genetic factors play some role in the cause; unlike other forms of leukemia, there are no clear occupational or environmental risk factors.

CLL/SLL presents most often in an asymptomatic individual with lymphocytosis found on a routine CBC or at times as painless lymphadenopathy. 

More advanced cases may present with splenomegaly, symptomatic lymphadenopathy, “B” symptoms like night sweats, fatigue, or weight loss, or as consequences of cytopenias such as anemia, recurrent infections, or bleeding. These are important components of the clinical staging of CLL (Rai and Binet staging).

The diagnosis is based on a persistent absolute B lymphocyte blood count >5,000 and clonality of the B cells confirmed on flow cytometry.

The natural history of CLL is quite variable, but since it is often an indolent condition, and given the lack of symptoms or cytopenias in this situation, close observation alone is recommended. 

Therapy is generally reserved for patients with advanced features as indicated above, or if there is rapidly progressing disease (e.g., when the lymphocyte doubling time is less than six months). 

Unlike other types of leukemia, there is no indication for bone marrow biopsy in most cases.

Although often an indolent disease, CLL can at times progress rapidly or transform into a high-grade malignancy (Richter transformation), and the risk of this occurring depends heavily on these cytogenetic results.

In addition, these markers are important predictors of response to treatment and useful in determining therapy selection when indicated.