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: email@example.com on behalf of Theresa Rohr
> Sent: Friday, February 23, 2007 8:14 AM
> To: Histonet@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
> 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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