Eighty-year-old man with rare chronic neutrophilic leukemia caused by T618I mutation: A case report and review of literature.

Background: Chronic neutrophilic leukemia (CNL) is a rare bone marrow proliferative tumor and a heterogeneous disorder. In 2016, the World Health Organization included activating mutations in the gene as one of the diagnostic criteria, with T618I being the most common mutation. The disease is often accompanied by splenomegaly, but no developmental abnormalities and significant reticular fibrosis, and no Ph chromosome and fusion gene.