Differential Diagnosis and Workup of Monocytosis: A Systematic Approach to a Common Hematologic Finding.

Basic studies have highlighted the phenotypic and functional heterogeneity in the monocyte compartment. Studies, both translational and clinical, have provided insights into why monocytosis occurs and how to distinguish the different etiologies. Flow cytometry studies have illustrated that monocyte repartitioning can distinguish chronic myelomonocytic leukemia, a prototypical neoplasm with monocytosis from other reactive or neoplastic causes. In summary, we provide an algorithmic approach to the diagnosis of a patient presenting with monocytosis and expect this document to serve as a reference guide for clinicians.