Myelodysplastic Syndromes/Myeloproliferative Overlap Neoplasms and Differential Diagnosis in the WHO and ICC 2022 Era: A Focused Review

SIMPLE SUMMARY: Myelodysplastic syndromes/myeloproliferative neoplasms (MDS/MPN) are entities that have been quite difficult to define since their discovery. At the time of presentation, they possess features of both myelodysplastic syndromes and myeloproliferative neoplasms. Because of this overlap, there has been an inherent difficulty in the diagnosis and classification of these neoplasms. The recent World Health Organization (WHO) 2022 classification and the International Consensus Classification (ICC) improved the diagnostic criteria for these disorders. In this review, we describe the main entities, highlighting the differential diagnosis. ABSTRACT: The myelodysplastic syndromes/myeloproliferative neoplasms (MDS/MPN) category comprises a varied group of myeloid neoplastic diseases characterized by clinical and pathologic overlapping features of both myelodysplastic and myeloproliferative neoplasms. For these reasons, these tumors are challenging in terms of diagnosis. The recent World Health Organization (WHO) 2022 classification and the International Consensus Classification (ICC) made changes in the classification of MDS/MPN compared to the previous 2016 WHO classification and improved the diagnostic criteria of these entities. The aim of this review is to describe the main entities reported in the more recent classifications, focusing on chronic myelomonocytic leukemia (CMML), MDS/MPN with neutrophilia (or atypical CML [aCML]), and MDS/MPN with SF3B1 mutation and thrombocytosis/MDS/MPN with ring sideroblasts and thrombocytosis. A particular emphasis is given to the differential diagnosis and analysis of subtle divergences and semantic differences between the WHO classification and the ICC for these entities.