Clinical presentation, progression, and outcome of patients with clonal B-cell counts of less than 5 × 10(9)/l, 5 to 10 × 10(9)/l, and more than 10 × 10(9)/l and chronic lymphocytic leukemia immunophenotype.

Objectives: The flow cytometric evaluation of peripheral lymphocytosis has led to a dramatic increase in the diagnosis of early stage chronic lymphocytic leukemia (CLL) and monoclonal B-cell lymphocytosis (MBL). Few studies exist to better delineate the natural history and differences between MBL and CLL.

Methods: Applying the recently updated B-lymphocyte threshold of 5 × 10(9) B lymphocytes/L for the diagnosis of CLL, we evaluated the differences in initial presentation, disease progression, time to treatment (TTT), and 10-year overall survival rates between patients with less than 5 × 10 × 10(9)/L, 5 to 10 × 10(9)/L, and more than 10 × 10(9)/L B cells.