The diagnostic criteria are determined by documentation of a MNP or myelodysplastic/myeloproliferative neoplasm with prominent eosinophilia and in some cases neutrophilia or monocytosis, or acute myeloid leukemia, or mixed-phenotype T- or B-lymphoblastic leukemia/lymphoma, and the presence of t(8;13) (p11;q12), or a variant translocation leading to FGFR1 rearrangements, evidenced in myeloid cells, lymphoblasts or both [10]. The gene discussed is FGFR1; the disease is acute myeloid leukemia.