ITGA4 and B-cell chronic lymphocytic leukemia: Moreover, several established CLL risk factors are also differentially expressed between the immunophenotypic subtypes of MBL; for instance, markers associated with aggressive CLL, such as CD38, ZAP70, and CD49d are highly expressed in the majority of ‘atypical’ MBL cases yet are rarely expressed in ‘CLL-like’ MBL (1, 5).