[Histonet] overfixation with formalin

[joelle weaver]

I have always been directed to the C. Fox article when discussing matters of the chemical mechanics and affects of aqueous formalin solution. Whenever I need to clarify a question, I tend to refer back to that resource. 




Joelle Weaver MAOM, HTL (ASCP) QIHC
 > From: gu.lang <@t> gmx.at
> To: histonet <@t> lists.utsouthwestern.edu
> Date: Sat, 3 Nov 2012 19:41:07 +0100
> 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
> 
>  
> 
> _______________________________________________
> Histonet mailing list
> Histonet <@t> lists.utsouthwestern.edu
> http://lists.utsouthwestern.edu/mailman/listinfo/histonet