Centromere 17: Spectrum green
HER2 locus: Spectrum orange
This is an image of a breast cancer sample stained by FISH. This sample is positive for amplification. There are 3 to 4 copies of the chromosome 17 centromere and 30 to 40 copies of the HER2 gene. The ratio of HER2 to centromere 17 is determined for each cell and an overall average ratio is determined. This particular case would be 35/3.5 = a ratio of 10. This is an amplification ratio of 10 which is highly amplified.