There are essentially no differences in the diagnostic criteria for the JAK2/MPL/CLAR-associated MPN and chronic eosinophilic leukemia between the two classifications, and both retain a category to place MPN that cannot be otherwise classified, but with slightly different names: MPN-NOS in WHO-HAEM5 and MPN-unclassifiable in ICC. Here, JAK2 is linked to Chronic Eosinophilic Leukemia, Not Otherwise Specified.