CCND1 probe labeled with an orange-red fluorescent dye and IGH green probe labeled with a green fluorescent dye bound to the target detection site by in situ hybridization. Under normal conditions (CCND1/IGH gene is not fused), it shows two orange-red signals and two green signals under a fluorescence microscope. When there is a gene fusion, the green and orange signals recombine to form yellow fusion signal.