Neoplastic causes of eosinophilia are often driven by genetic abnormalities and include: myeloid/lymphoid neoplasms with eosinophilia (MLN) that often involve genetic abnormalities such as rearrangements of PDGFRA, PDGFRB, and FGFR1, acute myeloid leukemia (AML) with CBFB::MYH11 fusion, and chronic myeloid leukemia (CML) driven by the BCR-ABL1 fusion gene [4–6]. The gene discussed is FGFR1; the disease is acute myeloid leukemia.