Distribution of different classes of CSF3R mutations and co-mutational pattern in 360 myeloid neoplasia

: The colony-stimulating factor 3 receptor (CSF3R) plays an essential role in differentiation, growth, and survival of granulocytes. Driver mutations in CSF3R gene represent a diagnostic marker of chronic neutrophilic leukemia (CNL). Less commonly, these mutations are observed in other myeloid neoplasms but their pathogenetic and prognostic role is still unclear. Here, we analyzed a large cohort of myeloid neoplasms to evaluate the incidence of CSF3R mutations and co-mutational profile. Mutational analysis was performed using targeted NGS myeloid panel in a consecutive cohort of 360 patients with myeloid neoplasms. Mutations in CSF3R were identified in 20/360 (5.6%) cases. A CSF3R gene mutation was present in 13/179 AML cases (7.3%), in 2/27 (7.4%) CMML cases, in 1/94 (1.1%) MDS cases and in 4/60 (6.7%) other myeloid neoplasms. The frequencies of patients with CSF3R mutations lowered to 2.8% in all cases and 3.4% in AML, excluding cases with variants of uncertain significance (VUS). A total of 23 mutations of CSF3R gene were detected, half localized in the extracellular domain, 5 in the transmembrane region (type I) and 6 mutations in the cytoplasmic domain (type II). In AML, CSF3R mutations were more frequent in patients harboring CBF alterations (25.0%) and CEBPA mutations (11.8%). Two cases with AML harboring pathogenic CSF3R variants were primary refractory to induction therapy. CMML cases with T618I variant showed a myeloproliferative phenotype. Overall, our findings support the notion that CSF3R variants, particularly type I and II pathogenic mutations, may modulate the phenotypic features of leukemic cells in myeloid neoplasia.