Introduction

Chronic lymphocytic leukemia (CLL) is the most common form of leukemia in adults in the Western world, accounting for nearly 25% of all leukemias with an estimated annual age-adjusted incidence of 3 per 100,000 persons in the United States. The median age at diagnosis is approximately 70 years, with 81% of the patients diagnosed when aged ≥ 60 years. Under the World Health Organization (WHO) classification, CLL is a B-cell neoplasm and the entity T-cell CLL has been reclassified as T-cell prolymphocytic leukemia (PLL). Recent data from the Surveillance, Epidemiology, and End Results (SEER) cancer statistics indicate that 5-year survival of patients with CLL is 73%.

Significant changes in the understanding and management of CLL have occurred in the last two decades. With the advent of newer treatment modalities, such as purine analogs and monoclonal antibodies, substantial improvements have been made in achieving complete responses (CR), with a proportion achieving molecular remissions and durable responses. Despite the advances in the treatment of patients with CLL, the majority of patients will relapse after primary therapy.

Diagnosis

The current diagnosis of CLL is based on minor modifications of the criteria originally proposed by the National Cancer Institute (NCI) (Table 5.1). A bone marrow evaluation is no longer required for diagnosis but is useful to determine the extent and pattern of involvement and to clarify the etiology of cytopenias.

The morphology and immunophenotype are adequate for diagnosis and to distinguish CLL from other disorders (Table 5.2).