HER2 Support Group Forums - View Single Post - her2 copy number cut-off point (by FISH) may be decreased (2.2to1.5)

Lani · 03-27-2009, 04:08 AM

The directions on how to do the FISH testing includes the following:

Scoring/interpretation
In our laboratory, we use PathVysion, a FDA-approved kit for HER-2 testing by FISH and follow the scoring and interpretation recommended by the manufacturer. In this procedure, the chromosome 17 centromere is marked with a green florescent signal and HER-2 gene with an orange florescent signal. Briefly, we assess 60 non-overlapping tumor cell nuclei and count the number of green and orange signals in each cell. Then, the overall gene-to-chromosome (17) ratio is calculated. A tumor is designated as “positive” for gene amplification if gene-to-chromosome (17) ratio is >2.0

Detailed procedure
We use FDA approved PathVysion kit to assess HER-2 by FISH. As per manufacturers’ recommendation, 20 tumor non-overlapping cell nuclei are enumeratedto obtain the HER-2/chromosome 17 ratio.

So if they count twenty cells and all are her2+ with orange fluorescent signal and there is no polyploidy of chromosome 17 so the ratio is 1: 1 ie,
one her2+ orange fluorescence per chromosome 17 green fluorescence the ratio is 20:2 or a FISH of 10, but it may also be that they count 2 chromosomes I think the highest I have heard of was around 10, but my memory may be failing me..

03-27-2009, 04:08 AM	#6
Lani Senior Member Join Date: Mar 2006 Posts: 4,783	theoretically, 20 The directions on how to do the FISH testing includes the following: Scoring/interpretation In our laboratory, we use PathVysion, a FDA-approved kit for HER-2 testing by FISH and follow the scoring and interpretation recommended by the manufacturer. In this procedure, the chromosome 17 centromere is marked with a green florescent signal and HER-2 gene with an orange florescent signal. Briefly, we assess 60 non-overlapping tumor cell nuclei and count the number of green and orange signals in each cell. Then, the overall gene-to-chromosome (17) ratio is calculated. A tumor is designated as “positive” for gene amplification if gene-to-chromosome (17) ratio is >2.0 Detailed procedure We use FDA approved PathVysion kit to assess HER-2 by FISH. As per manufacturers’ recommendation, 20 tumor non-overlapping cell nuclei are enumeratedto obtain the HER-2/chromosome 17 ratio. So if they count twenty cells and all are her2+ with orange fluorescent signal and there is no polyploidy of chromosome 17 so the ratio is 1: 1 ie, one her2+ orange fluorescence per chromosome 17 green fluorescence the ratio is 20:2 or a FISH of 10, but it may also be that they count 2 chromosomes I think the highest I have heard of was around 10, but my memory may be failing me..