RE: Her-2 and Zn Formalin


Dear Histonet,

DAKO recommends the use of formalin fixatives and encourages all labs to
request this as a standard fixative that is acceptable for HercepTest.
Report forms should indicate that results generated with other fixatives are
indeterminate due to improper sample collection but a score may be given due
to ethical considerations.  

Regarding the scoring false positivity, it is important to note that we do
not currently have a "standard" that defines definitively what a clear
positive and negative are.  This standard material is currently being
developed by a consortium of thought leaders in collaboration with the
National Institute of Standards and Technology.  DAKO is actively engaged in
the consortium to help develop appropriate standards.

Danielle Mach
Technical Service Specialist
DAKO Corporation, USA

-----Original Message-----
From: rueggp [] 
Sent: Monday, May 20, 2002 9:42 PM
To:; HistoNet Server
Subject: Re: Her-2 and Zn Formalin

I am not specifically aware of false positives with IHC related to ZN
fixation, but many alleged false + have been reported for IHC on NBF
which is recommended as the standard fix for DAKO hercept test.  ZN formalin
should not require as much HIER as it does not cross link the proteins as
as NBF.  Perhaps that would be the problem if one is doing the same HIER
methods for ZN formalin fixed samples that they do for NBF they may be over
I just attended the CAP Her2 conference in Chicago.  There is a campaign to
try and standardize her2/neu testing by starting with fixation.  It is just
too hard to compare results when different fixation and processing is being
Some of those reporting their IHC her2 test results thought that perhaps
can appear to be false + her2 may actually be real staining of some other
related protein.
Some thought that one must evaluate her2 staining using more criteria than
just the DAKO 1+, 2+, 3+ grading system.  Dr. Bloom from Rush in Chicago put
great deal of  importance in staining pattern and uniformity.  He
IHC stained cases that if strictly following the grading system would be
reported as 2+, but he claimed that he could tell by the lack of uniformity
staining that these cases would not show her2 gene over expressed by ISH,
indeed they did not, in his hands.  He tests for her2 by IHC and by FISH on
100% of his cases and has a lot of data to back up his findings.
The issue of false + or false - staining, at least for IHC methods, needs a
lot more investigation and data comparing IHC to ISH and most importantly to
treatment outcome.  ISH methods for gene over expression are also not fool
proof and things can go wrong with that assay as well (false + &-).  It is
never that simple, is it?  I will be writing a synopsis of the CAP Strategic
Sciences Her2/neu conference for the Journal of Histotechnology.
Patsy Ruegg wrote:

> Is anyone aware of false positives with Her-2 testing on Zn Formalin fixed
> breast?
> Thanks
> Ronnie Houston
> Regional Histology Operations Manager
> Bon Secours HealthPartners Laboratories
> 5801 Bremo Road
> Richmond, VA 23226

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