Fluorescence in situ hybridization (FISH) for ALK gene

Fluorescence microscopy image using ALK break apart probes of cells from a NSCLC tumor, demonstrating an ALK gene rearrangement. The red and green probes hybridize to regions that flank the highly conserved translocation breakpoint within the ALK gene. Arrow: In the setting of an ALK rearrangement, these probes are separated, and splitting of the red and green signals is observed. In the wild-type intact ALK gene, the closely apposed red and green probes result in a yellow signal.