If either PDGFRA, PDGFRB, FGFR1, or JAK2::PCM1 gene rearrangement is identified, the diagnosis should be classified as “myeloid or lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions”; eosinophilia may be a clue to this alternative diagnosis. This evidence concerns the gene JAK2 and Increased total eosinophil count.