The nuclear export protein, XPO1, is mutated in less than 5% of cases of chronic lymphocytic leukemia (CLL). Most frequently these mutations affect codon Glu571. Cases of CLL with mutations in XPO1 tend to be associated with a higher prevalence of CD38 expression (>30% of tumor cells), ZAP70 expression (> 20% of tumor cells), concomitnat NOTCH1 mutation and unmutated IGHV. Given the low prevalence of XPO1 mutations, prognostic signficance has not been firmly establlished. XPO1 has been successfully targeted in some experimental models of CLL.