PDGFRB and atypical chronic myeloid leukemia, BCR-ABL1 negative: Cytogenetic analysis, FISH, and a lack of typical myeloproliferative neoplasia rearrangements (BCR-ABL, PDGFRA, PDGFRB, FGFR1, and PCM1-JAK2) and mutations (JAK2, CALR, and MPL) are necessary to confirm the diagnosis of aCML.