# Expanding the Spectrum of CSF3R-Mutated Myeloid Neoplasm Beyond Chronic Neutrophilic Leukemia and Atypical Chronic Myeloid Leukemia: A Comprehensive Analysis of 13 Cases

## TL;DR

This study shows that mutations in the CSF3R gene are not only found in chronic neutrophilic leukemia and atypical chronic myeloid leukemia but also in other myeloid neoplasms, highlighting the need for broader molecular testing.

## Contribution

The study expands the known spectrum of CSF3R-mutated myeloid neoplasms beyond established categories and identifies distinct clinical and molecular features.

## Key findings

- The CSF3R p.Thr618Ile mutation was the most common alteration observed in 11 out of 13 cases.
- MDS/MPN cases had the highest median variant allele frequency and were associated with mutations in epigenetic and splicing regulators.
- Acute leukemia cases showed mutations in JAK3, STAT3, and NRAS, with distinct survival patterns across diagnostic groups.

## Abstract

Background: Genetic alterations in CSF3R, typically associated with chronic neutrophilic leukemia (CNL) and atypical chronic myeloid leukemia (aCML), rarely occur in other myeloid neoplasms. Methods: This study characterized the clinical, morphologic, cytogenetic, and molecular features of 13 patients with non-CNL non-aCML myeloid neoplasms with CSF3R alterations. Patients (median age, 77 years) were categorized into groups with a myelodysplastic/myeloproliferative neoplasm (MDS/MPN) (n = 5), acute leukemia (n = 4), and other myeloid neoplasms (n = 4) based on the WHO 2022 and ICC criteria. Results: The CSF3R p.Thr618Ile mutation was most frequent (11/13), with additional pathogenic variants including p.Gln743Ter and frameshift mutations affecting the cytoplasmic tail. Variant allele frequencies (VAFs) ranged from 2% to 49%, with the highest median VAF in the MDS/MPN group. Co-mutations varied by subtype; MDS/MPN, NOS, and CMML cases frequently harbored mutations in epigenetic regulators (ASXL1, TET2) and splicing factors (SF3B1, SRSF2, ZRSR2), while acute leukemia cases showed alterations in JAK3, STAT3, and NRAS. Survival analysis revealed distinct patterns across the three diagnostic groups, with MDS/MPN having the poorest prognosis. Conclusion: This study expands the recognized spectrum of CSF3R-related myeloid neoplasms and highlights the clinical and molecular heterogeneity associated with these mutations, emphasizing the need for comprehensive molecular profiling and the potential for targeted therapies.