[Histonet] overfixation with formalin

[Rittman, Barry R]

Gudrun
I  would thank him for his opinion and move on.
There has always been the unfortunate tendency to accept anything that is published or presented formally as if it were gospel.
I am a lot more skeptical, give me proof.
Barry
________________________________________
From: histonet-bounces <@t> lists.utsouthwestern.edu [histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Gudrun Lang [gu.lang <@t> gmx.at]
Sent: Saturday, November 03, 2012 1:41 PM
To: histonet <@t> lists.utsouthwestern.edu
Subject: [Histonet] overfixation with formalin

Hi histonetters!

I'm just attending a histo-course, where the teacher told us his opinion
about overfixation.

For him overfixation takes place in any formaldehyde solution with a
concentration above 5%. This should cause the margin-artefact, that leads to
false-positive IHC at the margins of the tissue and to false-negative
results in the center. The higher concetrated fixative should harden and
shrink the surface, so it cant be penetrated any more by the fixative.



I told him about the publication of Cecil Fox, who saw shrinkage only in
solutions with formaldehyde concentration above 30% (I think) and said, that
the methanol-part is responsible for that.

I believe, that these margin-artefacts are due to drying at the time of
biopsy or an effect of the needle-shot itself. (But believing is no
evidence)



In our lab we use 8% formaldehyde as standard fixative, buffered with
low-molar phosphatebuffer. There are no complains from the doctors about
margins.



Please help me with the histonet-wisdom. What's your opinion?



Bye

Gudrun Lang



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