Chronic lymphocytic leukemia: Diagnosis and clinical staging

Chronic lymphocytic leukemia (CLL) is defined as B-cell count ≥5.0 × 109/l with a typical CLL immunophenotype (CD5+, CD19+, CD20+ [weak], CD23+, CD79a+ and low-density monoclonal surface immunoglobulin). Small lymphocytic lymphoma is biologically and genetically identical to CLL, but lacks lymphocytosis (circulating B-cell count of <5.0 × 109/l). It presents as malignant tissue infiltration, typically causing lymphadenopathy, hepatomegaly, cytopenias and/or disease-related symptoms. Monoclonal B lymphocytosis is defined as a clonal B-cell condition with circulating B-cell count <5.0 × 109/l, without adenopathy, hepatosplenomegaly, cytopenia or disease-related symptoms. CLL/small lymphocytic lymphoma is likely to be subdivided into cytogenetic categories as our understanding of disease biology improves.