sentences:  In certain rare hematological cancers, the fusion of "FGFR1" with various other genes due to Chromosomal translocations or Interstitial deletions create genes that encode chimeric FGFR1 Fusion proteins.These proteins have continuously active FGFR1-derived tyrosine kinase and thereby continuously stimulated the cell growth and proliferation.These mutations occur in the early stages of myeloid and/or lymphoid cell lines and are the cause of or contribute to the development and progression of certain types of hematological malignancies that have increased numbers of circulating blood eosinophils, increased numbers of bone marrow eosinophils, and/or the infiltration of eosinophils into tissues.