Help understanding FISH report please

[Cheryl]

Can someone help me understand the bottom line here please? I have called the path lab, asked my onc how to decifer this etc... Just can't seem to understand how 3+ is arrived at. Thanks.

FISH performed using the Vysis PathVysion DNA probe set the HER-2/neu (17q11.2-q12) and the centromere region of chromosome 17 (CEP 17; 17p11.1-q11.1). Seventy interphase cells of invasive carcinoma were scored. Resulting numbers expressed as a ratio of HER2/neu:CEP 17.

OK, so here is the interpretation:

This tumor demonstrated heterogeneity in the degree of HER2/neu amplificaiton. Some tumor cells show no amplification, with a ratio (60 cells scored) of 1.2. A minority of cells seen on scanning show amplilficaiton of HER2/neu, with a ration (10 cells scored) of 5.5. These findings are interpreted as representing amplification of HER2/neu in a small proportion of cells within this specimen.

I understand the 5.5 is what indicated overamplification. But what about the use of terms "a minority of cells (10 cells showing amplificaiton vs. 60 not)" and "a small proportion of cells within this specimen".

Thanks so much to anyone who can help me understand this. 3+ is handwritten on the page next to this report.

[kk1]

Cheryl;

What the report is saying is that only a few of the cells tested showed amplification of the her2 gene. This is also why they use the term heterogeneity meaning mixed.

The report says they looked at a total of 70 interphase cells ( Non-replicating phase of cell cycle) from the tumor. In 60 of the cells (93%) there was no amplification, but in 10 of the cells (7%) they did find amplification of 5.5 eg. There were 5.5 more copies of the gene than would be expected in these 10 cells.

As I understand it, generally the high the percentage of cells showing her2 amplification the more aggressive the tumor tends to be. The fact you have a low % is a good thing, however the fact that ANY of the cells show ANY level of amplification means that you would likely benefit from herceptin. This is why sometime Dr. may use a simple postive(any cell showed amplification) or negative(no cells were amplified) FISH.

KK1

[Cheryl]

Thank you so much for putting this in discernable english for me! I am on Herceptin, even though I was stage 1. Do you have a medical background to be so knowledgeable?

[kk1]

Hi Cheryl;

Always glad to help. No I am not a medical person just an environmental scientist with an advanced degree in molecular biology. Most of these medical tests are based on standard techniques only the specific probe for the protein, cell, or DNA changes. FISH stands for Fluorescence (glows in the dark) In Situ (done on intact cells) Hybridization (joins probe and target) it is a DNA gene test.

I realized I never answered your 3+ question. The other, and oldest her2 test is referred to as IHC, it stands for Immuno-Histo Chemistry, and is a type of protein receptor test using fluorescently labeled antibodies to the her2 receptor protein that sits sticking out on the membrane of the tumor cell. The more receptors your tumor cells have the more of these labeled antibodies will bind to the cell and the brighter the cell will appear in the microscope. A reading of 3+ means the cells bound a lot of antibody probe and so you have a lot of her2 protein receptors on the tumor cell surface. A 3+ means you will likely benefit from Herceptin, which by the way like the probe for the IHC test is also an antibody that latches on to the receptor and blocks it from being active and prevents the cell from growing and replicating.

But the IHC test is an older test and the problem is that sometimes you get what is called non-specific binding so a cell might glow faintly eg. you get a reading of <2+. A low reading could mean that the cell is expressing low levels of the her2 receptor or just simply that your cells are a bit “sticky” and it is a false positive. So now they generally recommend the more expensive FISH DNA test if you have a low score on the IHC in order to figure out if it is a false positive or not. The logic being that if you have multiple copies of the her2 gene then the cell is very capable of making lots of extra her2 receptor protein even if it doesn’t happen to be caught in the act of expressing it at the moment of the IHC test. If the cell doesn’t have extra copies of the her2 gene then it can’t possibly make lots of the protein so the IHC <+2 means that it is a false positive and herceptin would not be very useful. Since the FISH DNA test is relatively new some doctors might not have understood what the meaning of the gene amplification (number of copies) score meant but they should be familiar with what an IHC 3+ meant. Good pathologists probably got in the habit of also writing IHC3+ on the report to ensure that the Doctor reading it would understand what to do e.g. give you herceptin ;)….it’s all about communication!

Glad to hear you’re on Herceptin. Guess I should log off and go brave the gas station and grocery store again to stock up for Wilma---we’ve been waiting for this one for so long that I am low on gas and milk again. Just hope it hurrys by with little damage so that I can take my Herceptin on Wednesday. Keep those poor people in Cancun in our prayers they must be getting hammered.

KK1

[Cheryl]

kk1 - I hope others are reading this too. There is a lot of confusion over this. You must be in Florida. I have family in Naples and Pensacola. Those in Naples went to relatives in Atlanta already. Best wishes and our prayers to you, and thank you again so much for taking so much time to explain what you understand so well.