I would add a word of caution to the answers above. It depends on the markers you want to detect. Some may be very stable, but we know some for which the expression can decrease after a month or so. So I would try not to delay the staining too much. Of course if all the samples are treated the same way it will have less of an effect on results. We tend to keep unstained slides in a box in a refrigerator, just so we know the conditions are more constant than at RT.

You can store paraffin cut sections on slides in ordinary slide boxes at room temperature in a shelf or bench for several years and you can do IHC without any problem. Nothing to worry on that issue. Do not refrigerate or freeze these slides.

Thank you very much Subhash, this sounds wonderful.

I have stored slides with paraffin sections for months and was still able to do RNA FISH on them, so IHC would not be a problem. If they are infiltrated properly, they are very stable. I would just make sure they are protected from dust and kept in a controlled environment (ex a grade in the middle of a Florida summer would be a bad idea). I wouldn't worry about the stability too much if you plan to work through them in the ext month or two.

Thanks Daniel !

I would add a word of caution to the answers above. It depends on the markers you want to detect. Some may be very stable, but we know some for which the expression can decrease after a month or so. So I would try not to delay the staining too much. Of course if all the samples are treated the same way it will have less of an effect on results. We tend to keep unstained slides in a box in a refrigerator, just so we know the conditions are more constant than at RT.

Ok, thanks Jean-Martin !

Thanks, Matthew!

I agree with Matthew and Jean-Martin, while in the block the tissue is sealed from the open air but once it has been cut the air can access the exposed parts of the section to cause oxidation. Oestrogen receptor is a well known antigen that can lose reactivity just a week after being cut, for repeat-ability cutting just prior to staining will ensure less variability.

Thank you Chris.

I totally agree with Jean Martin and Matthew!

Thanks Maria.

I agree with both Jean-Martin Lapointe and Matthew.

I would like to add a few more information about the stability of FFPE tissue section/block. Most of the commonly analytes are quite stable in blocks at 4 degree Celsius for over a year for their subsequent detection by IHC staining method. However, such a stability can not be attained in pre-cut tissue section on slides, particularly those which have been baked. Therefore, I recommend that you store the section on slides at 4 degree Celsius for no more than 1 month and baked them just prior to conducting IHC staining.

Sounds good!! I'll do that Ashraf. Thanks !!

Yes, in my experience for ki67 stainings in paraffin blocks, there is a less intensity in my older paraffin blocks as compared to the newly embedded colon sections.

I experienced this issue for ki67 only.

solution1: we can also store our paraffin blocks in 4 degree refrigerator to sustain the better antigen signal for a bit longer duration.

solution2: And if you enough number of mice, just have new tissue in freshly embedded paraffin blocks.

Thanks, Naveen. I think storing the blocks in a refrigerator is a great idea.

If you looking for normal staining (eosin & hematoxylene) you can store your slides for long time but for IHC your antigenicity will lose with the increase in time (eg. astrocytes markers)