Since the publication of the latest World Health Organization (WHO) classification in 2008, there has been a significant effort for clarification of unresolved questions, especially with the help of the rapidly developing field of molecular genetic studies, next-generation sequencing in particular. Numerous entities within the WHO categories of myeloproliferative neoplasms (MPNs) and myelodysplastic (MDS)/MPNs have been extensively studied, with large published series attempting to characterize and better define their morphologic and molecular genetic features. This emerging genetic landscape maintains a robust correlation with the various disease entities recognized by the WHO classification scheme based on a careful integration of detailed clinical information, bone marrow and peripheral blood morphology, immunohistology, and genomics. This brief review summarizes the current guidelines as they apply to diagnosing both the classical BCR-ABL1 negative MPN (polycythemia vera, essential thrombocythemia, and primary myelofibrosis) and the more common subtypes of MDS/MPN overlap syndromes. The more important recent molecular updates as well as the upcoming changes to the current WHO classification, expected to be published in late 2016, will also be briefly reviewed.