Recent studies suggest that approximately 4% of the general population over age 40 harbor a population of clonal B-cells with the phenotype of either CLL or another low grade NHL. The biologic characteristics and clinical implications of MBL have begun to be defined and appear to differ based on whether it is identified during the diagnostic evaluation of lymphocytosis or incidentally discovered through screening studies using highly sensitive detection methods. Additional research into the epidemiology, biology, and natural history of MBL is needed (Table 5). The majority of individuals with MBL will not develop a hematologic malignancy.
