Hi Julio,

I can speak to a research / core setting where I often advised my users to
place their tissues in 70% ethanol following adequate formalin fixation to
maintain epitopes for potential downstream IHC studies. I have found tissue
can be placed in 70% and maintained indefinitely. They do not 'unfix'.

Recently though I was speaking to a pathologist who doesn't like that
protocol as she sees nuclear changes in tissues that have been in 70% for
extended periods.

So, yes, I think that idea is good in principle. I would say that the staff
time taken, and extra reagent costs, of changing all those biopsies over
into another solution, plus the additional chemical waste generated is not
worth simply making sure the original formalin containers are well sealed
after grossing  and / or purchasing one of those specimen collection
cupboards that filters the air coming through.

I do understand the dangers of formalin, but considering how much of it is
in use and how many of us on this list have been exposed to it for the
majority of our lives and we are still OK! (well, maybe, I suppose that
depends on your definition of OK is :)

Leica seem to think this is OK too!

Ultimately you would have to perform studies to check the effects on your
downstream processes and proof this procedure in your own lab.


On Sun, Oct 16, 2016 at 10:57 AM, Julio Benavides via Histonet <
histonet@lists.utsouthwestern.edu> wrote:

> Hi there,
> This is me again with formalin issues. The health and safety officer of my
> institute keeps on in her crusade of eliminating formalin from the world.
> After your helpful emails, I convinced her that you do need formalin to fix
> samples, other approach would need to much setup IHC protocols.  Then and
> with good intention at heart, she has suggested that, one possible solution
> to reduce formalin presence in the institute could be, once samples have
> been fixed in buffered formalin (10%) and embedded in wax, to substitute it
> by 70% ethanol until the sample is discharged. Has anybody tried anything
> similar? What do you think? Would it be possible to come back to formalin
> in case of necessity (let´s say we want to retrim fixed samples after they
> have been in ethanol 70% for 5 months… would you trust them for IHC? HE?).
> Thanks again for your help
> Julio
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Caroline Miller (mills)
Director of Histology
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