Additionally, other WHO-defined neoplasms, including all other MPNs, CMML, aCML, and especially myeloid/lymphoid neoplasms with eosinophilia and gene rearrangement of PDGFRA, PDGFRB or FGFR1, need to be excluded, and no PCM1-JAK2, ETV6-JAK2 or BCR-JAK2 fusion, blasts ≥ 20% or inv(16)(p13.1;q22), t(16;16)(p13.1;q22), or t(8;21)(q22;q22.1) are allowed for a diagnosis of CEL [134]. This evidence concerns the gene JAK2 and atypical chronic myeloid leukemia, BCR-ABL1 negative.