The World Health Organization (WHO) classifies myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions (MLN-TK) as those driven by translocation of genes such as PDGFRA/B, JAK2, FLT3, ABL1 or FGFR1.1 MLN-TK neoplasms are highly aggressive and feature increased risk for progression to acute leukemia. The gene discussed is FGFR1; the disease is lymphoid neoplasm.