[Histonet] Extended time in paraffin

Bryan Hewlett bhewlett <@t> cogeco.ca
Fri Feb 23 13:19:43 CST 2007


The original questioner mentioned so called 'overfixation' and asked how to 
prevent the possibility.

If you, or anyone else, think that a fixation time just anywhere in the wide 
range of 8-48 hours constitutes standardization,
the word needs to be totally redefined!!!


----- Original Message ----- 
From: "Weems, Joyce" <JWEEMS <@t> sjha.org>
To: "Bryan Hewlett" <bhewlett <@t> cogeco.ca>; "Monfils, Paul" 
<PMonfils <@t> Lifespan.org>; <histonet <@t> lists.utsouthwestern.edu>
Sent: Friday, February 23, 2007 1:55 PM
Subject: RE: [Histonet] Extended time in paraffin

>I believe this has to do with the new FDA ruling rather than "overfixing" 
>as we think of it. It just has to do with standardization. j
> -----Original Message-----
> From: histonet-bounces <@t> lists.utsouthwestern.edu
> [mailto:histonet-bounces <@t> lists.utsouthwestern.edu]On Behalf Of Bryan
> Hewlett
> Sent: Friday, February 23, 2007 1:29 PM
> To: Monfils, Paul; histonet <@t> lists.utsouthwestern.edu
> Subject: Re: [Histonet] Extended time in paraffin
> Paul,
> Ahh! the voice of reason!
> No kidding, even 5-7 days or more won't 'overfix' because there is NO such
> thing as 'overfixation' in NBF.
> Bryan
> ----- Original Message ----- 
> From: "Monfils, Paul" <PMonfils <@t> Lifespan.org>
> To: <histonet <@t> lists.utsouthwestern.edu>
> Sent: Friday, February 23, 2007 1:18 PM
> Subject: RE: [Histonet] Extended time in paraffin
> Personally I don't believe that a couple of days in formalin will 
> "overfix"
> anything, and large fatty tissues like breast and colon specimens can only
> benefit from additional fixation time. That having been said, if you do 
> want
> to limit the fixation time, why don't you program the processor to keep 
> the
> tissue in the fixative in station 1 for the desired length of time, then 
> go
> into an extended 70% ethanol in station 2, where the tissue can be held
> safely for as long as necessary before proceeding into 95% ethanol and the
> rest of the cycle on sunday night as usual.
>> ----------
>> From: histonet-bounces <@t> lists.utsouthwestern.edu on behalf of Theresa Rohr
>> Sent: Friday, February 23, 2007 8:14 AM
>> To: Histonet <@t> lists.utsouthwestern.edu
>> Subject: [Histonet] Extended time in paraffin
>> I have a problem with processing breast tissue over a weekend. Breast
>> tissue is run in a separate processor from our Sugical and endo 
>> specimens.
>> We do not have weekend staff. We usually run a two day delay with the
>> processing starting Sunday night and both processors ending early Monday
>> AM.
>> The current guidelines suggest this delay of breast tissue sitting in
>> formalin could result in over fixed breast tissue.  The pathologists want
>> to end the cycle on Saturday but we have no staff here to remove and/or
>> embed the tissue. The pathologists themselves would have to remove the
>> cassettes from the paraffin!
>> The questions are what can they do with these cassettes? Again, the 
>> tissue
>> is breast tissue, mainly cores or target blocks or tumor that may need 
>> IHC
>> and/or FISH on diagnosis
>> 1.  Can they just leave the cassettes on the processor in warm paraffin
>> (60 degrees) from Saturday until Monday?
>> 2.  Can they remove them from the paraffin and let them harden at room
>> temperature and then be heated, melted and properly embedded on Monday?
>> 3.  Can they put the cassettes in a container of warm paraffin "to cover"
>> and then let the whole container solidify and on Monday Histo melts the
>> container, removes the cassettes and embeds?
>>  I have only found two clear commentaries.
>>  Sheehan and Hrapchak who say extended time in paraffin will cause
>> shrinkage and hardening. There is also a reference in Carson, saying
>> tissue should remain in paraffin the shortest time necessary for good
>> infiltration as prolonged heat causes shrinkage and hardening.
>> Can any of you offer me any further references and/or assistance or your
>> own methods/experiences?
>> Thank you so much for your time and assistance
>> Theresa Rohr
>> Nyack Hospital, NY
>> rohrt <@t> nyackhospital.org
>> Theresa Rohr, BA, HT(ASCP)
>> Section Head, Histology
>> Nyack Hospital
>> 160 North Midland Avenue
>> Nyack, New York 10960
>> phone 845-348-2276
>> fax 845-348-8430
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