MDS/ MPN with neutrophilia, until recently called atypical chronic myeloid leukemia (aCML), being part of the myelodysplastic/myeloproliferative neoplasms is a very rare disease with poor prognosis. Although emerging data reveal its cytogenetic and molecular profile, integrated survival and treatment data remain scarce. We analyzed a cohort of 347 adult patients diagnosed with MDS/ MPN with neutrophilia, registered in the Netherlands Cancer Registry between 2001 and 2019. Our demographic baseline data align with other cohorts. We observed cytogenetic aberrations exclusively in patients aged >65 years, with trisomy 8 being the most common abnormality. We identified 16 distinct molecular mutations, with some patients (16/101) harboring up to 3 different mutations; ASXL1 being the most frequent one (22%). In a multivariable Cox regression analysis, only age, hemoglobin level and allogeneic hematopoietic stem cell transplant (alloHSCT) were associated with overall survival (>65 years of age HR 1.85, P=0.001 and alloHSCT HR 0.51, P=0.039). As no other treatment modality, seemed to impact survival and might cause toxicity, we propose that all patients eligible for alloHSCT should whenever possible receive an allogeneic transplant. It is imperative that we strive to improve outcomes for patients not eligible for alloHSCT. Tackling this challenge requires international collaborative efforts to conduct prospective intervention studies.