Myeloid/Lymphoid Neoplasms with Eosinophilia and Tyrosine Kinase Gene Fusions (MLN-eo-TK) represent a distinct and heterogeneous group of hematologic malignancies characterized by recurrent gene fusions involving tyrosine kinases, such as PDGFRA, PDGFRB, FGFR1, JAK2, FLT3, ETV::ABL1 and other partner genes/variants. The gene discussed is PDGFRB; the disease is hematologic disorder.