Introduction: Low absolute lymphocyte/monocyte ratio (LMR) at presentation has been associated with clinical outcome in various types of hematological malignancies including multiple myeloma, Hodgkin's and non-Hodgkin's lymphomas, but to the best of our knowledge, no data are available on its role in acute myeloid leukemia (AML). This study aims to investigate the prognostic significance of LMR at diagnosis, as a simple biomarker merging an index of host immune homeostasis with tumor microenvironment, in de novo AML. Methods: In this prospective cohort study, we evaluated 100 previously untreated adult patients with de novo non-M3 AML, aged 18 years or older and treated at Clinical Hematology Unit, Internal Medicine department at Zagazig University Hospitals, from September 2016 to August 2019. The estimated initial LMR cut-off value for survival outcome generated by receiver operating …