OBJECTIVETo review the implications for diagnosis, pathogenesis and potential for new therapeutic option for chronic neutrophilic leukemia (CNL).

DATA SOURCESData cited in this review were obtained mainly from PubMed and Medline from 1993 to 2013 and highly regarded older publications were also included. The terms "chronic neutrophilic leukemia" and "diagnosis" were used for the literature search.

STUDY SELECTIONWe identified, retrieved and reviewed the information on the clinical and laboratory features, the new genetic findings, prognosis and disease evolution and management of CNL.

RESULTSThe discovery of high-frequency granulocyte-colony stimulating factor receptor (CSF3R) mutations in CNL identifies a new major diagnostic criterion, and lends more specificity to the World Health Organization (WHO) diagnostic criteria for CNL, which are variably applied in routine clinical practice.

CONCLUSIONSIn patients for whom the cause of neutrophilia is not easily discerned, the incorporation of CSF3R mutation testing can be a useful point-of-care diagnostic to evaluate the presence of a clonal myeloid disorder, as well as providing the potential for genetically informed therapy. The oncogenic CSF3R mutations are molecular markers of sensitivity to inhibitors of the SRC family-TNK2 and JAK kinases and may provide a new avenue for therapy.