[Histonet] HER2-related issues


Dear colleagues,

I've been reading the postings on HER2-related issues. Allow me to  
address the fixation-related issues.

1. Overfixation: 48 versus 72 hours of fixation has no difference on  
the impact of protein or gene signal. The CAP guidelines will most  
likely be revised to increase the upper limit of cutoff to 72 hours.  
That said, overfixation seems to have some impact on hormone  
receptors, and given that every invasive breast cancer should be  
tested for both HER2 and hormone receptor, then people will need to  
address the upper limit of fixation time.

2. Undrefixation: This what really has had devastating effects on the  
quality of HER2 testing by IHC. The literature is there, but it's the  
usual, good-old literature published by Fox and others in the 80s and  
90s. Everyone knows that formaldehyde penetrates the tissue at a very  
rapid rate of 1 mm/hour (more or less depending on fat content and  
other factors). But infiltration is NOT equal to fixation. The 6-hour  
minimum fixation requirement should be strictly adhered to. There is  
currently a loop hole in the minimum requirements for fixing core  
biopsies versus excision specimens. Cores are required to be fixed  
for a minimum of 1 hour. That will change to. The revised guidelines  
will most likely increase that to 6 hours. This is a very realistic  
and scientifically sound requirement.

We wrote a document to help colleagues address various issues related  
to the impact on the guidelines on their lab. It can be found on our  
website (www.vitromolecular.com).


Hadi Yaziji, M.D., Medical Director
Vitro Molecular Laboratories
Ancillary Pathways
7000 62nd Avenue, PH-C
Miami, FL 33143
T 305-740-4440
F. 786-513-0175

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