This is a very good point, Rene. However, ...
Prolonged exposure to melted paraffin (in 60 degrees) may be as bad
(or most likely worse) than overfixing in formalin.
Each time a standard parameter is drastically changed (such as over-
exposure to dehydration or melted paraffin), that component NEEDS to
be validated when it comes to predictive markers assay. I'd much
rather validate 72-hr fixation than having to validate prolonged
exposure to components of the tissue processor.
Immunohistochemistry of predictive markers needs to be treated
differently than diagnostic markers. It should be done with maximum
care so we can tell the oncology community that the results our labs
are producing are reliable and trustworthy. This is the essence of
HER2 guidelines. The minute we start deviating from a pre-analytical
parameter, the minute we start getting into trouble. In fact, if
people have been fixing their speciment according to the FDA-approved
fixation range of 6-24 hours, we wouldn't have been in the mess we're
in right now.
On Jan 24, 2008, at 11:46 AM, Rene J Buesa wrote:
> Not if you set the instrument to start EXACTLY when you want. You
> will have the tissues in melted paraffin more time, or you can
> extend the dehydration times. You can do a lot of things all
> preventing longer fixation in NBF. Modern TP are very flexible
> instruments and I have no data that reflects any deleterious effects
> for the tissues' reactive qualities or sectioning characteristics
> after being in melted paraffin for long periods of time.
> René J.
> firstname.lastname@example.org wrote:
> I agree with Rich, and it's good to hear that some colleagues have
> started their own mode of cross-validation.
> If you choose to deviate from the upper fixation limit of 48 hours,
> you will ONLY be at default if you do not have evidence (with
> documentation) that raising the upper fixation limits to 72 or 96
> hours has no detrimental effects on the results. The CAP will
> eventually increase the upper limit to 72 (or hopefully 96) hours once
> there is solid evidence that is ok to do so.
> Rene's suggestion to put the instrument on delay is not a valid
> solution. As long as the tissue is sitting in formalin in the
> instrument while it's on delay, it's still being fixed. This issue was
> discussed at the ASCO/CAP meeting.
> Hadi Yaziji, M.D., Medical Director
> Vitro Molecular Laboratories,
> President, Ancillary Pathways
> 7000 SW 62nd Avenue, Suite Penthouse-C
> Miami, FL 33143
> Tel 305.740.4440
> Fax 786.513.0175
> This email message, including any attachments, is for the sole use of
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> Message: 18
> Date: Thu, 24 Jan 2008 09:57:05 -0500
> From: "Richard Cartun"
> Subject: Re: [Histonet] HER2neu Fixation times
> To: "Ramona Turner" ,
> Message-ID: <479860F2020000770000A527@gwmail4.harthosp.org>
> Content-Type: text/plain; charset=US-ASCII
> Personally, I would not initiate any drastic changes at this point.
> Keep in mind that these are guidelines; however, you must validate
> your testing if you are going to follow other fixation guidelines. I
> think everyone knowledgeable with this issue knows that the problem is
> with underfixation, not overfixation. I recently pulled tumor out of
> formalin after 8 months of fixation and the IHC was still "3+" and the
> FISH showed beautiful amplification (ratio of 10.0). I hope that once
> the scientific evidence is evaluated, these guidelines will be
> changed. Major expense is being incurred here unnecessarily. How is
> your concordance between IHC and FISH for the detection of HER2? If
> it's not broken, don't try to fix it. Our "ad-hoc" committee on IHC
> standardization is meeting in Santa Barbara on Sunday and I hope this
> issue will be discussed.
> Richard W. Cartun, Ph.D.
> Director, Immunopathology & Histology
> Assistant Director, Anatomic Pathology
> Hartford Hospital
> 80 Seymour Street
> Hartford, CT 06102
> (860) 545-1596
> (860) 545-0174 Fax
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