[Histonet] overfixation with formalin
Edwards, Richard E.
ree3 <@t> leicester.ac.uk
Wed Nov 7 09:38:18 CST 2012
I have seen far more damaged/unusable (apart from H <@t> E) tissues through under-fixation than over-fixation.....................
From: histonet-bounces <@t> lists.utsouthwestern.edu [mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Gudrun Lang
Sent: 03 November 2012 18:41
To: histonet <@t> lists.utsouthwestern.edu
Subject: [Histonet] overfixation with formalin
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
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?
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