PDGFRB and Chronic Eosinophilic Leukemia, Not Otherwise Specified: In the SM-CEL patient, Janus kinase 2 (JAK-2) gene mutations, rearrangements of the platelet-derived growth factor receptor (PDGFR) α and β genes, and T-cell clonality were ruled out, while genetic analyses for the fibroblast growth factor receptor 1 (FGFR1) gene were not performed.