A detectably labeled DNA FISH probe comprises detectably-labeled nucleic acid molecules from the 8p11.23 chromosomal region and from the 2q35 chromosomal region. The probe is a FISH probe capable of detecting a fusion between the FGFR1 and FN1 genes. A patient having a disease associated with a FN1-FGFR1 gene fusion may be treated by: detecting translocation of a portion of the FGFR1 gene to the FN1 gene using chromosomal FISH probes, and treating a patient with said translocation and gene fusion with 1) a drug which inhibits FGF 2) a drug which inhibits FGFR1, and/or a 3) drug which targets a signaling pathway associated with FGFR1.
