This study also confirmed the low frequency of CSF3R mutations in AML (later reaffirmed by Beekman et al., finding a prevalence of CSF3R mutations of <0.5% in a series of 1446 consecutive cases of de novo AML124), and their absence in B-cell and T-cell ALL as well as in reactive neutrophilia14,76, suggesting that the CSF3R mutation represents the defining molecular lesion in CNL. The gene discussed is CSF3R; the disease is chronic neutrophilic leukemia.