[Histonet] overfixation with formalin

[Tony Reilly]

Hello
 
I agree.  I recently saw presentation at a conference where a lab received specimens from Kiribati located in a small group of remote islands in the pacific.  They receive specimens in all sorts of solutions including sea water.  He was able to demonstrate good staining in specimens that had been in conc. 37% formaldehyde (no buffer) for 3 months simply by modifying antigen retrieval.  Of the 55 antibodies they stain in their lab there were only 2-3 where staining was not achieved.  But if they were underfixed!!!
 
regards
Tony
 
 
 

Tony Reilly  B.App.Sc. , M.Sc.
Chief Scientist, Anatomical Pathology
Pathology Queensland-PA Laboratory 
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Health Services Support Agency | Queensland Health
 
Level 1, Building 15,Princess Alexandra Hospital
Ipswich Road,WOOLLOONGABBA  Qld4102
Ph: 07 3176 2412
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Fax: 07 3176 2930
Email: tony_reilly <@t> health.qld.gov.au
Web:  www.health.qld.gov.au/qhcss/
 
 


>>> "Edwards, Richard E." <ree3 <@t> leicester.ac.uk> 11/8/2012 1:38 am >>>
I have  seen far  more  damaged/unusable (apart from H <@t> E)   tissues through under-fixation than over-fixation.....................

-----Original Message-----
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

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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