Eosinophilia is present in almost all cases of MLN-TK, caused by fusion genes involving a receptor [PDGFRA or B, fibroblast growth factor receptor (FGFR), fms like tyrosine kinase 3 (FLT3)], a transcription factor (ETV-6), or a non-receptor kinase (Janus kinase 2, JAK2). This evidence concerns the gene FLT3 and Increased total eosinophil count.